"You do ever just want to do something stupid… and AWESOME?"
It was tempting to leaves it as it was, but oh well.
Demyx is the Melodious Nocturne, ninth member of Organization XIII. The Organization is a group of Nobodies, who are beings without hearts and are therefore incapable of emotion. They try to use Kingdom Hearts to get their hearts back, but destroy worlds in the process.
For the most part, he’s not a particularly useful or well thought of member. While in the Organization, he often complains about having to work and how he’d much rather just play his sitar. It’s to the point where even Roxas and Xion make fun of him for it. He only goes on a few missions with Roxas, all of which… he basically shoves on number XIII.
He meets Sora first in the Underworld, where he is seen… running away. It turns out he was running from a giant three-headed dog, so it was for a good reason. Once Sora defeats said dog, he runs into Demyx again, who proceeds call him ‘Roxas’ and has to read off of a cue card to remember that he’s supposed to be ‘liberating his [Sora’s] true disposition.’ And then complains about how is totally not the right guy for this, which no one believes after being made to destory a hundred water clones in a minute.
He doesn’t appear again until Hollow Bastion, where he cheerfully greets Sora and then gets yelled at and told to move. He acts like he’s very hurt by all this, but eventually the facade breaks down and he fights for real. Even with his somewhat goofy demeanor he presents a very hard battle, but it eventually defeated and is consumed by a pillar of light.
To be added: basically, he does stuff, plays music, sings, kicks Axel's butt, makes friends, gets a heart, becomes an Angelli, and other things.
While at one point the fact that he was a Nobody would mean that any personality he put on was false. In Nautilus this has changed- he has a heart, and therefore emotions, but still acts basically as he did as a Nobody. He's carefree and lazy, preferring to play his sitar than work any day. He often whines about being a bad fighter, or just that he doesn't like to. While the not liking it part is true, he is a more than capable fighter and can hold his own. He's just a coward and prefers to run away. He loves music and sharing music. While he didn't really have any friends in canon, he has made some in Nautilus and really likes them.
His heart has added some complications to his personality- namely, the guilt of sort of knowing that what the Organization did was not very nice. He has gradually worked up the basics of psychological development, now at the point where he's learning the difference between good things to do and bad things without having to rely on the aftereffects of how he feels. His work ethic is continuing to grow- he's actually been working a lot more in practicing Bending and everything than he used to, he just doesn't tell anyone because he thinks then they'll make him actually use it.
He controls water, as well as being able to summon a sitar from thin air. He also is in charge of the Dancer Nobodies. While he technically can summon the dark corridors, he has not for a quite a while- partly because Nautilus isn't that big and partly because the darkness could corrupt his new heart very easily.
Forms: Robot (transforms into a speedboat), goldfish, dog, dogfish
Angelli training: He can now move very quickly in order to run away from fights and is working towards teleporting. He really likes this power.
Bending power: He has learned how to manipulate ice, fire, light, and is starting to work on earth, and has learned how to bend emotions into people through music
Bold indicates currently in Nautilus.
I ~ Xemnas: The Superior of Organization XIII. Demyx is… kind of not sure how to feel about Xemnas at this point. Because, on the one hand, Xemnas is and always has been 'scary' in his mind. (He's also the only person Demyx calls 'sir' because calling Xemnas by his name is weird.) On the other hand, the Organization has disbanded, and Xemnas hasn't really done anything, and if everyone else is changing why couldn't he? But he's certainly not going out of his way to find out much about his former boss.
II ~ Xigbar: The Freeshooter. Demyx gets along with Xigbar pretty well, though the last time Xigbar was in Nautilus Demyx ended up having to fight him.
III ~ Xaldin: The Whirlwind Lancer.
IV ~ Vexen: The Chilly Academic. Demyx mostly tried to stay out of Vexen's way when he was in Nautilus, as he finds him very cranky.
V ~ Leaxeus: The Silent Hero.
VI ~ Zexion: The Cloaked Schemer.
VII ~ Saix: The Luna Diviner. Saix is still pretty scary, especially since the only times he's had a heart around Demyx have made him either violent or angry. Or both.
VIII ~ Axel: The Flurry of Dancing Flames. Their relationship is… interesting. In Nautilus, Demyx started off not really liking Axel (because he's a traitor B|) when he didn't have a heart and was still a mildly sneaky bastard, and now it's… something very different. There has been SO MUCH development in their relationship that it's kind of insane. It went from 'oh you're a traitor' to 'kind of friends' to 'hey I'll actually help you out in a fight' to 'friends \o/' to '…sort of dating???'
Currently, Demyx has no idea how he feels about Axel. First and foremost, Axel is still his friend, and that isn't likely to change anytime in the near future. The 'sort of dating' has obviously changed things a bit, to the point where Demyx thinks he should be feeling a change in the relationship. But honestly, he hasn't yet. Axel is still his friend, and ok so now sometimes Axel pushes him against for reasons other than yelling at him and if he ever really found out about Sideswipe's constant flirting that would probably annoy him BUT. While things have changed, they're pretty nice changes, and the stuff that was important to him hasn't gone away. So he's really ok with how things are right now, even if he's… still unsure about why he's ok with it.
X ~ Luxord: The Gambler of Fate. Demyx is actually sort of ok with his arrival. Luxord's not nearly as scary as some of the other members.
XI ~ Marluxia: The Graceful Assassin. Demyx doesn't know Marluxia's a traitor. Haha, whoops.
XII ~ Larxene: The Savage Nymph. When she was in Nautilus, Demyx somehow managed to knock her unconscious and tie her up. Kinky. She returned to Nautilus with no memory of being there before, which made Demyx very glad. But then she tried to cuddle him when she was high, which was very creepy.
XIII ~ Roxas: The Key of Destiny. They didn't talk much before Nautilus (and when they did, Demyx was usually shoving off missions onto him) but in Nautilus they've talked quite a lot and Demyx has made some effort to help out. However, Demyx is very careful about what he says, because he knows if he tells Roxas anything he shouldn't, Axel will kill him. Roxas keeps leaving and coming back, which kind of bothers him a bit since he keeps making FRIENDS with the one that's here and once he leaves all that tends to go away. And starting over is hard.
XIV ~ Xion: He has no idea who she is, and only knows that she exists through Roxas. He doesn't know WHY he doesn't remember her, but has decided not to worry about it. He hasn't talked to her much.
Ienzo: Aww, he's adorable! Though kind of mean. Demyx still hasn't figured out that this is Zexion's other.
Namine: He didn't know Namine really well before her arrival, and they only bonded briefly during the high as a kite event when they were the only sane ones in Org Base.
Riku: He has a keyblade. That's… pretty much all Demyx knows about the guy.
Sora: He isn't sure what to think of Sora, since, you know. Keyblade Master. He's mostly been avoiding him.
Alexander Wolfgang: Demyx hasn't seen Alex in a while, and they didn't talk too much anyway (for a variety of reasons), but to Demyx he seemed like a really cool guy with good taste in music. He'd like to hang out with him some more and have another jam session if… he knew where the guy was.
America: Considering how long both of these guys have been in Nautilus, it's kind of surprising that it took so long for them to talk.
Death: Yes, the guy who runs away from fights is friends with Death. When Demyx got killed by Teatime, he hung out with Death for the week. He likes Death's cats much better than Saix!cat.
Hatsune Miku: Miku is an honorary member of the Organization now, and has managed to bend herself a body. He finds the fact that she 'adopted' the loaf of bread with his face on it kind of disturbing, but she's really sweet and he likes talking to her.
Jonathan Teatime: The dude that killed him. He doesn't know that yet, though.
Lysander: They weren't really acquainted until after Zanki's death, and have mostly bonded over that. Fell back into Sleep.
Micheal Trinity: The only person other than Larxene that Demyx can say with confidence that he hates. Guy called him a hack. ;-;
Pearl: He met Pearl during the Heartless attack, and she's expressed an interest in music since they've meet and asked him to teach her.
Ratchet: Giant robot! Knew him vaguely as one of Sari's friends, until the Nobodies took a trip to get Roxas's arm fixed. Thinks he's pretty nice. They've become decent friends at this point, probably being some of the only people in Nautilus to want to rock out after a while.
Sari Sumdac: Was one of his first friends in Nautilus, and helped in bending him his heart. He still likes talking to her when he can, but she's way more active in the city than he is.
Wendy Moira Angela Darling: Was one of the the friends who helped him bend his heart. Technically, he recognized her from his own encounters in Neverland, but she had no recollection of Sora to heartless to his knowledge. Returned to Nautilus with memory intact, believing she'd only been gone a day.
Zack Fair: Zack is probably the first 'real' friend Demyx has ever had. And when they became best friends, well. It confused the hell out of him, but it wasn't unwelcome. (He still has a little trouble with the idea of having multiple best friends, since the only example he knew before was Axel and Roxas, so when Cloud showed up he got a little worried. But it's turned out ok, and he's starting to figure out that it is possible.) There are a lot of things he still doesn't understand about Zack (like AGH WHY DO YOU LIKE WORKING AND PUSHUPS DX), but he likes the differences and has learned a lot from Zack on what it means to be responsible and help people out, even if there's a risk for you. He doesn't always IMPLEMENT this knowledge, at least not to Zack's degree of it, but he is learning and starting to pick up on these things. Zack is one of the most important people to him in Nautilus, and one of the few he'd do most anything to help.
Zanki: No longer in Nautilus. Was one of Demyx's friends that helped him bend a heart while in Nautilus. They went surfing together. When he died, Demyx received his Onka- it is said to be a symbol of justice, discipline, and fighting spirit. Demyx finds it cruelly ironic that he possesses none of those, but takes care of it should Zanki ever return.
To be added: ???