Tetsuo Takahashi

The main protagonist. A biology teacher who is fascinated by Demi and wants to learn more about them. He is occasionally referred to as "Iron Man" by his students, a pun on his bulky physique and his name. As he learns about Demi, he starts to understand the problems they face, both as teenagers and Demi, and he strives to help them, wherever he can.

(Source: Wikipedia)