Name:
-Ryo Takeshi
-Thunder
Age:
-16 (Ryo)
-Unknown (Thunder)
Gender:
-Male (Ryo)
-... sounds like a guy atleast. (Thunder)
Race:
-Human (Ryo)
-Nexoid (Thunder, also a made-up race)
Personality:
-Ryo: Ryo is an overall upbeat and friendly boy with a strong sense of justice and an empty head, often coming off as sort of an idiot, reflected in his nature to rush into things without thinking about the consequences. As a result of his upbringing under his sister and a whole bunch of superhero shows, Ryo doesn't hesitate in helping out those who need it and has almost gotten himself killed on more than one occasion.
-Thunder: Unlike Ryo, his companion is much more down-to-earth, most likely to point out Ryo's idiocy, mainly through a snarky/sarcastic comments. Nonetheless he does have his nice side and does care about Ryo, seeing as he stuck around for 10 years practically raising the kid.
History: 10 years ago, Ryo had come home one day to find that his house on fire. Upon being told that his parents may not have survived, Ryo had run off, not stopping until he had gotten far away. When he had stopped, he stumbled upon a chance encounter with a strange creature called a Nexoid that had taken the form a floating yellow orb with eyes. After naming the Nexoid Thunder, and although he wasn't amused by the somewhat silly name, the strange being took up residence in Ryo's left eye, becoming a valuable friend and allowing the two to merge together.
Anything notable after that is irrelevant to what is happening in the present. Ryo's time at TJA all begins with a dream...
Appearance:

Other: While Ryo has little to no power on his own, by merging with Thunder, he (obviously) gains the ability to use electricity, in addition to incredible speed, though he more often than-not forgets that he has that second ability while in combat, often resorting to using his electricity in different ways.
Thunder is a Nexoid. Nexoids are a sort of weapon-like creature created and sealed long ago, typically when they're awakened, they don't have a concrete form, so they take on a form based on the imagination of the human they bond with. With Thunder, he took on the form of a floating yellow ball with eyes when he met Ryo at the age of 6, as Nexoids tend to take on more simpler forms when exposed to younger minds.. Once a contract is formed between the Human and Nexoid, they gain the ability to merge together, a form once again determined by the Human host's imagination. For Ryo and Thunder, this was more detailed than with Thunder's awakening, since they didn't have their first fusion until Ryo was 10.
Finally finished that CS.
Most likely not so great, but hell why not give it a try?
Also, credit to Goldi for the amazing picture of these two. I apologize if this doesn't meet your expectations by the way.
I'll also write up a race sheet for Nexoids if required.