Masaru

A man of very few words - tends to put on a very serious face most of the time.
He's very nice, actually, and will immediately apologize if he realizes he's hurt someone with his words [except for Rin];
He gets embarrassed when he has his animal ears and tail out (especially his ears), so he avoids being seen with them;

Rintarō teases him often, and has a special nickname for him too - Misa;