Такахаші Тецуо

The main protagonist. A biology teacher who is fascinated by demis 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 demis, he starts to understand the problems they face, both as teenagers and demis, and strives to help them in any way he can.

(Source: Wikipedia)