Information \o/
character name: Kou
canon source and the point from which they're taken: Monochrome Factor, Post chapter 40 of the manga
character's age: Old! Rei don't age physically, but he looks like he's in his 20's.
canon powers, skills, pets and equipment: Since Kou is a Rei, he has quite a few powers. Rei exist to help maintain the balance between the shadow and light worlds, specifically they are aligned with the light world, thus Kou's skills are mainly for doing this. Even when he is in his human form, he has much greater strength and speed than the average person, and he is able to handle a loooot of fighting without taking much damage himself. This comes in handy, as Kou's part-time job seems to involve beating up men involved in underworld dealings, but he never seems to have any trouble with taking on multiple people. This resistance to taking damage also helps when he is punched or kicked down the street for being a pervert at cute girls. He's normally quite agile, and his dramatic abuse at the hands of irate girls appears to be nothing more than an act, since he just springs right back up after being hurt. This agility and skill also lends itself to Kou being able to handle getting to great heights quite easily, as he is seen sitting on steel beams that are part of the construction of a high rise building.
On the more human side, Kou is also quite handy with other questionably useful underworld skills, as his entire flat has utilities that he doesn't pay for. He's managed to get free water, electricity, and every other utility he could possibly need, stating that the only thing he pays for is propane tanks. He is also adept at first aid, since he is shown to have stitched up an injury that cut all the way through his hand, and a deep wound on his abdomen by himself.
When Kou is in his Rei form, he is able to do many other shiny things! His outfit, a sort of white suit with buckles and belts/straps on the arms and legs is part of his weaponry. He is able to manipulate the straps to grab or whip things, or to entangle creatures and subdue them with... suit bondage? Er. His hands also become covered with 'claws'; what look like sharp, jointed metal plates cover each finger. These can be used to tear and rip and grab anything that Kou is fighting. He also has Batman-like tendencies to hang upside down from any available structure where he can hook his feet. He is also able to move between the different worlds without difficulty.
His fighting skills obviously come in handy in Rei form as well, as Kou is normally able to take out many shadow monsters by himself. Another part of his Rei powers is his ability to suck the darkness, the basic unsavory, "bad" element of the shadow world, out of people that have absorbed too much of it and been overtaken. His already longer-than-normal canines grow even longer, and he bites the affected and literally drinks the darkness out of them. This apparently has no adverse affect on him other than that it tastes terrible and can give him a slight stomachache. Kou is also able to place seals on a person to lock the darkness within them away and keep them free of its influence.
In both forms, Kou can smell a variety of things that aren't normally noticeable, such as a creature's smell from a great distance. He is also able to put people into a brief sleep with just a touch, as well as altering the memories of people if he needs to. Some of these are obviously a bit hax so I wouldn't be having him do things willynilly; most of these would need player consent anyway.
As for equipment, Kou doesn't carry much more than his glasses, cigarettes, lighter and the odd fashion accessory or some cash.
personality: One of Kou's nicknames in canon is "Puppy". Of course, this nickname was given to him by someone that he doesn't even like, but it does capture aspects of his personality quite well.
At heart, Kou wants nothing more than to serve Ryuko, his king, faithfully and forever. Nothing would make him happier than to have Ryuko back, both so that he can act as the kind of person he believes he always should have been for Ryuko, and so that he can feel better about his betrayal in running away from him. When he is in his more serious mode, which happens when he speaks seriously of Ryuko or is in front of him, he is quite formal and docile; he speaks from his heart and is nothing if not obdenient. He truly adores his king, and even without being ordered to, he'll work tirelessly to ensure that he does everything he can to make Ryuko proud of him and to feel worthy of serving him.
To that end, Kou takes on a very big brother role for Akira, the reincarnation of Ryuko. He is everything that a cool older brother should be; suave, funny, teasing and completely forgiving of deviant behavior because he is involved in things he shouldn't be too. He is very comfortable with Akira and Ken; he cheerfully teases Kengo about being a virgin and hiding his dirty magazines in his room in front of everyone else. He freely ruffles Akira's and Ken's hair, drapes on them, and hangs out with them at his place whenever they come over. Kou even has nicknames like Akira-chan for them, and encourages them to do things like skip school if they want to. This doesn't earn him many points with anyone else, but Kou doesn't mind. He also looks out for them, if they're having trouble with anyone or anything. He readily tells Akira that he can always count on his big brother Kou to protect him and his friends. He doesn't mind that they know about his part-time work, and he has never tried to get Akira and Ken to stop getting in fights, either.
Kou's big brother side and his pervert side are what he typically shows everyone else too. When he first meets Aya, he doesn't feel any shame in lifting her skirt to see what kind of underwear she has on, or commenting out loud about her choices in panties. This earns him a slight beating, but he shows no remorse and actually flirts with her more when she jumps at him because she is scared of ghosts. It seems as though he's being more playful than actually trying to make a move on her. Kou also has no problem with saying things that he knows will annoy someone he doesn't like; he does this most often with Shirogane, since he doesn't like him anyway. Even while doing it, he acts innocent of any wrongdoing. Kou also sometimes enjoys pouting and acting very put out when someone does call him on his immature actions, but a minute later it's as if he's forgotten all about it.
While he prefers to maintain the cheerful big brother act, Kou can also become very serious when the need arises. Most often, this occurs when he is either fighting Kokuchi or doing something like trying to turn Ken back into his normal self after he absorbs a lot of darkness. He's still slightly playful, but he is also a lot more focused on getting his job done and making sure that it's done quickly. He'll focus a lot more on what he needs to do, to the point of telling someone that he doesn't have time to deal with them, even when he knows they might take the opportunity to attack him as well. He also fights quite seriously, using any means necessary in order to win, and not giving up even if things are looking difficult for him.
A different side of this is Kou's temper, which he rarely lets show. The one time it really gets the best of him is when another enemy, the one who apparently actually carried out the murder of Ryuko, mentions Ryuko's name. Kou's whole demeanor changes. His face contorts with rage and he screams at Sawaki that he doesn't want to hear Ryuko's name out of his mouth. This is pretty much the only time Kou completely loses his temper, but it does go to show how angry and serious he can become.
Kou's fierce loyalty not only comes through when he loses control of his temper like that. It also shows up in his inability to completely forgive himself for betraying Ryuko, even though Ryuko told him himself that he never thought of him as a traitor. Although he doesn't typically show it, he does still blame himself for what he's done in the past. Little moments of introspection don't hit him too often, but when they do, they really get him.