Now, before I give you some background on the OC's I would like to mention that choosing to use Het pairings made the challenge harder, because honestly you could make a bulleted list of the way these band members interact with each other and you'd find things to fit the table prompts easily. How they interact with girls on the other hand is entirely different. I tried to use a bit of psychology to match the band member to a suitable fem character, and actually I'm pretty happy with them.
In terms of background, what I did with them typically was make at least one girl into something of a female attachment to the bands. Seeing as they all have at least one song where there's a female back up singer, I just took that role and made it a little less back-up-y, and then the other roles are usually filled by friends of the singer girl, or actresses in PV's, and friend's of actresses in PV's etc. (Also some of the pairings' OC's are based off my favorite almost-canon yaoi pair)
The GazettE:

Reita x Kitty ~ Kitty's the fem vocal attachment to the GazettE. She's shorter than Ruki and similarly sweet, and the hallmark of her relationship with Reita is that they both have such striking and strong personalities that that are continually arguing over something. He's brash and crude and idiotically straight forward, she's too sensitive and assertive. Kitty is also addicted to sweet things, utterly addicted to sweet things.

Aoi x Meisa ~ I based her exceptionally loosely on Kuroki Meisa, the catty and strong, yet simultansously sweet and caring aspects of the singer. Also Meisa, like Kuroki-san, is an independent singer with a solo career that has more than once crossed paths with Kitty, making them good friends by this point. Meisa is drawn into the GazettE's world because of her association with Kitty and as she's the only cool headed one of the lot, she and Aoi are drawn together as their friends act like idiots. They have their own eccentric quicks of cutely stupid behavior, as well.

Ruki x Maki ~ I based her exceptionally loosely on Horikita Maki (not that she and Ruki are really suited to each other), or more specifically, a few of the characters that Horikita-san has played. Maki is an actress, friends with Kitty initially through Miesa (because Maki & Meisa in the real world are close friends, so naturally . . .), and soft beyond reason, and stupidly righteous and assertive of everything she believes in, while shy and squishy when she isn't trying to save the world.

Kai x Nana ~ Nana's an entertainment reporter that's been friends with Meisa, Maki, and Kitty forever, at least since her first article when she was just an intern. She's been brought on to give Gaze & Kitty interviews and get special inside stories because of her friendship with Kitty. She and Kai fit nicely together because she might be on the soft innocent side of  things, but she's also her own brand of crazy that keeps Kai guessing and gives his motherly tendencies an outlet. Nana also happens to be a premier fanfiction writer and frequently dreams of Gaze stories that star her closets friends, stories that most of them read avidly and demand to have more of. Nana's currently attending TSA in prep for an American venture to learn about the US's famously free journalism.

Uruha x Leslie ~ Nana's BFF from TSA. She's a sporty soccer freak that has spent extensive time in England despite being an American by nationality. She & Uruha are basically the inverse of Kitty and Reita. Leslie is the blunt and aggressive one while Uruha is the whiny diva, both are rather crass and short tempered and will strongly defend their opinions, even when they've been proven wrong. When Uruha does actually get to prove that he can be masculine serious sometimes, she's goofing off with a soccerball. He's the one that gets her to dress in anything other than shorts and a t-shirt and their arguments are really more bickering than anything, unlike Reita and Kitty, who argue viciously on a daily basis.
Alice Nine:

Tora x Namie ~ She's based exceptionally loosely on Amuro Namie, mostly because having her be based on Amuro-san gives Namie a past career, fully established with reference points and everything, and songs that I don't have to make up. Namie is a strong willed, assertive sweetheart. She bickers constantly with Tora over everything (almost as a super toned down version of Reita & Kitty's arguments), mostly for the fun of it. He's said that he wants to be able to protect his girlfriend (I don't have a link to cite it, but there are at least two distinct interviews of it), but Namie isn't really in to being protected. She's soft enough underneath her strong personality to need protecting, but she fights Tora every inch of the way. Namie and Tora balance out, each taking on what the other can't do without even a hint of collaboration, it's just natural. They both have cats and they both think that their cat is the bast cat in the world even though to anyone else they'll just complain about something or other in their animals. Namie's hooked up with Alice Nine for a while, working with them on her new song, and on theirs, and then she just never really left.

Saga x Yuuki ~ Yuuki is the name I'm giving to every girl that's ever acted in an Alice PV . . .  she's sweet and straightforward and completely unabashed in her friendliness and trickest antics. She keeps Saga on his toes, both challenging him at every turn and entertaining him between. She also confronts his insecurities that others hardly even notice, and he in turn gets to be the solid figure in her life. As an actress she'd dealt with too many people, in character and out, that don't keep to one compass and she finds comfort in Saga's steadfast craziness.

Nao x Mira ~ Hiroto once said that Alice would invite the most skilled person covering Gemini to a live, and that Nao would pay for his/her ticket. Well, they did. Mira reinterpreted the song for several different instruments and the video went viral enough to catch the PSC coordinator's eyes. She hadn't meant for it to go like that, she just loved the song, and she felt really bad forhaving prompted Hiroto into making Nao pay for her backstage pass and was appologetic to him the whole time. He being his sweet self, tried to soothe her, and somehow they landed on the topic of video games and the rest is history. She's one of the unaverage sort of girls that really can't be convinced of it and is shy beyond reason, especially in the face of Alice Nine's bold personalities. Nao makes her feel special, and she gives Nao a bit of sanity amidst Alice's antics.

Shou x Erika ~ Erika is Mira's friend. She's straight forward and engaging, not shy at all and looks after Mira in general. She's crazy enugh to mess around with Shou without tiring for an instant. She's on the pessimistic side of things though, and rather disnchanted with the world. She's fascinating to Shou and he to her. They spend most of their time trying to convince each other of their own point if veiw. Erika has the same self esteem issues Mira does, but rather than having grown shy from it she'd gone defensive. A part of their courtship thing is based off the Number Six PV, for reference. Underneath it all though, she really wants to believe in what Shou does, and his singing helps her to do that.

Hiroto x Chisa ~ Chisa is also friends with Mira, and with Erika. She's the boldest and most brazen of the trio. She neither believe in nor believes false the notion of everyone being good people and their being love for everyone, she just doesn't really care. She's out to enjoy herself and will do so whether or not those around her are enjoying it with her. She's bold enough to keep Hiroto on his toes, and crafty enough to annoy him in ways he never thought he could be annoyed, all in good fun. Her energy bounces off of him and together they're almost constantly hyper. She's also got a quiet side though, one that makes Hiroto's protective and sincere side show more often then he'd like to admit. And in turn, Chisa can get Hiroto to smile even when it's the last thing in the world he feels like doing.
Antic Cafe:

Yuuki . . .  doesn't exist . . . for this challenge I have made him Bou in disguise. Yes, I know he isn't. He's nothing like Bou, physically or by personality. But that doesn't really mean much at the moment. For starters, we know next to nothing about him, which makes him damn near impossible to fic accurately, and I really tried to peg the true personalities of the band members. Besides, I absolutely cannot even pretend to ship anything other than Bou x Kanon and if I wanted to make that an active pairing with an active An Cafe and Takuya . . . well, somebody had to go, and Yuuki was the best option . . .

Kanon x Bou ~ Obviously. They're my only yaoi pairing in this challenge. I don't even need to explain them. Though I will say that the reason Bou left in my world was a combination of the most popular theories. A) he felt like he was lying to his fans because the overly cutesy personality he had on stage wasn't his whole self and it was eating him up inside. B) he had a falling out with his family and was depressed, hence the reason that the guilt of lying began to hurt even more. & C) he wanted to go back to school, he was lazy and a terrible student the first time around but he wanted a fresh start After he got over-ish being depressed and all and came back to Kanon, and AnCafe, he wanted a lot of fresh starts, with Kanon, with the Band, with himself as a person etc. Miku was the one that came up with the idea of Yuuki (since he is the one that first found him if interviews can be believed).

Takyua x Akira ~ Akira sometimes lives on the floor above Takuya, literally right above him. She is a girl with a very rough past and meets Takuya by coincidence. Despite her past, she is charming and cheerful, and intrigues Takuya beyond measure. He also feels instinctively protective of her as she apparently needs protecting. His relaxed and comparatively down to earth nature comforts Akira when she needs it and doesn't pry. Her mystery keeps him interested and her circumstances keeps him feeling protective. Also for her role in aiding Bou at school, Takuya feels naturally indebted to her from the beginning.Theirs is a relationship of circumstance, developing through external changes, both to Akira's life and Takuya's and as his bandmates' relationships develop.

Miku x Riri ~ Riri is a roadie for An Cafe (she really exists, but I don't actually know anything about her, so my Riri isn't really based of of the real one . . .) and had been great friends with Miku since forever it seems. She's bold and adventurous and constantly curious. She's also unbelievably patient and sweet when working with someone that needs it, nursing both Bou and Akira through their rough spots. At the same time she's perfectly willing to goof around, her peculiar sense of humor bouncing in strange sync to Miku's as they joke around with things that just go over everyone else's heads.

Teruki x Hitomi ~ Hitomi is the girl next door, almost literally. She was Teruki's near neighbor through all of his school years, sweet and grounding but exciting enough to handle his strangest antics. She was the one that first encouraged him to take his talent of tapping and turn it into drumming, and the one that always encouraged him to join and to persevere with An Cafe. He's always been her support, helping her chase her dreams by going after his own. He's sweet and entertaining and better than a best friend. They've got a 'best friends that really is much more' thing that takes them much longer to notice and admit than Miku & Riri, as their relationship had always been vaguely flirtatious.
LM.C:

Maya x Miya ~ Miya is a girl with a rough past, but one she's mostly managed to escape from. She's childish and aggressive in a way suited to dealing with and encouraging Maya. They steal things from each other, particularly lollipops and outerwear clothing (like hats and hoodies), and live for their music. Everything aside from their friends and their music bores them and they quite litterally with do anything to get out of the boring stuff. This often involves taking each other on crazy adventures with conveniently forgotten cell phones. He's the petulant one and she's the sassy one, they argue over everything except their addiction to sugar and the fact that Aiji is a diva and a nag. She's motherly to her best friend and often forgets to take care of herself, but Maya can usually coerce her into doing something vaguely good for herself. She's the new support bassist for LM.C (jun and ken and denki and whatnot everyone decided they had something terribly pressing to do . . . yeah I never really came up with a suitable explanation for that, but I didn't feel like coming up with fics and pairs for everyone), but she plays at least a dozen instuments and jams with Maya for the heck of it on random sets around the studio. They're the friends that were always more, and they work out as such just perfectly.

Aiji x Haruki ~ Haruki is Miya's best friend and the support drummer for LM.C. Aiji keeps Maya in check and Haruki tempers Miya. Haruki's terribly soft, her only hint aggression coming out in her drumming, and Aiji is often disarmed by that, having dealt with the overly aggressive Maya for most of his 'caretaker' career. Miya looks after Haruki for the most part, but after having gotten used to keeping Maya alive, Aiji starts extending his care to Haruki. She's a ball of contradictions, a soft drummer, the restraint on Miya and the one that needs caring for. She keeps him interested and he stands as her only sane friend. They gravitate towards each other and like what they find in a much softer relationship than their friends'.
ViViD:

Koki x Kira ~ Koki is much more aggressive than most people give him credit for, even as he is unbearably sweet and adorable. The dichotomy throws Kira off a bit when she's brought on as a female vocal attachment for ViViD. She's not an independently famous singer of any sort, she was brought in by PSC specifically because all of their other bands were getting femme figures and the company wanted to give ViViD the oportunity to expand their fanbase as well. She's confident in her own abilites as far as singing and even acting fanserivce goes, but when the unand games carry backstage, she's a bit out of her element. Koki tries to make her feel at home with the band, but usually ends up making her feel even more disoriented. Their romance developes slowly, but Koki makes it clear from the beginning that he likes girls like Kira and wants to get to know her better for that reason.

IV x Reina ~ One of Kira's closest friends, Riena works at the same talent agency as Kira. In their dynamic duo, Reina is the agressive one, and absolute refuses to admit that she has a crush on IV to anyone but herself and Kira. She acts accordingly as well, being all coy and flirty with him after having admitted to herself that she's crushing, and refusing to let the fact that she's crushing turn her all cutesy and whatnot, pretending to the rest of the world that she's not at all bothered by his sweetness, humor, or perfect looks becuase she refuses to admit to him that she's crushing.

Reno x Ayame ~ Ayame is Reina's old friend, she also works for the same talent company, and even more agressive than Reina. She's a model as opposed to a singer, so confidence in herself has been instilled for a long while. She's frequently brought onto ViViD PV sets and photoshoots to boost the fanservice because Kira's only really able to pull it off while actually on stage. Ayame often simply bursts onstage when Kira's having problems now and again due to the fact that ViViD's femme attachment is much less well-recieved than the others of PSC. Ayame's personality is strong and focused enough to handle Reno at his most leaderly and his most puppy-ish sliding between coy and captivating with ease. She and Reno bicker ina flirty teasing way right from the beginning and they never look back.

Shin x Saya ~ Typically sweet, straightforward, and confident, Shin becomes all shy and jittery around Saya initially because of her apparent kindness and soft personality, and then because of the teasing of his bandmates conspiring against him. Saya's Ayame's old school mate and current good friend, tagging along wherever she goes, curious and adventuresome even though she's shy around strangers (Ayame usually takes care of talking to anyone they don't know). Saya's also close to Reina and therefore Kira, she and Kira make quick friends due to their shared woes of having best friends that are occsionally more than they can handle. She gets a quick crush on Shou when she meets him, having already liked him as a vocalist before meeting him. They're the cutely awkward couple that is only made more awkward by the others' attempts to make them less so.

Ryouga x Yui ~ Yui is Saya's school mate, the one that brings sense to the rest of the group as a whole. Ryouga simply doesn't know how to handle her. She's ridicuously friendly, even when he's giving off the coldest vibe known to man. Though Ryouga is a goofball at hear and messes around with his friends beyond the limits that 'maturity' dictates, around new people or even those he doesn't see interacting with his friends very often, he's shy and protectively cold to avert the fact that he's simply awkward in many social situations. Yui doesn't care, and she even able to pick up on the little cues that Ryouga makes in reference to her one-sided converstations to get to know him almost as well as his friends do. Their relationship is fairly straight forward once it gets started, he grows more and more comfortable with her, and she lets him be who he is because she knew his true self all along. This pairing is written about the most in my ViViD one-shots, but only the very beginning of their relationship and many years along the line . . . no inbetween at all, because it's exceedingly uneventful, really.