Tetsuo Takahashi

 is a main character in Demi-chan wa Kataritai.

Personality
A Biology teacher by profession, he holds an innate interest in demi-humans for their unique existence. Despite his curiosities regarding demi-humans, his gentle nature lead him to value their struggles and bonds in adapting to human society over anything else as time goes by.

Several demi-humans have taken interest in him as he does not display the more apparent reactions that most humans give when presented with demi-humans' unique physiology; or at the very least, he forces himself to hide his fear, lust, and other primal instincts for the sake of prioritizing these demi-humans' well-being.

A welcoming face, stocky build, and kind heart made him quite the reliable father figure to many that knows him well.

Yuki Kusakabe
Tetsu helped Yuki realize her demi nature as a snow woman posed no harm to others.

Sakie Satou
Tetsu treats Saki like anybody else (as he represses his normal reactions to her aphrodisiac effect) to make her feel more comfortable (since she is always jumpy about being around men.) He tends to feel uncomfortable when Saki is around (but doesn't show it).

History
He attended the Musashino University of Science

Trivia

 * His nickname, "Iron Man," comes from a pun based on his first name; in Japanese, "tetsu" means "iron" and "o" is usually used for "man" or "person", and this nickname is likely reinforced by the fact that he is built like a tank.