|Birthday||April 11, 1997|
|Relations||Komari Koshigaya (younger sister)|
Natsumi Koshigaya (younger sister)
Yukiko Koshigaya (mother)
AppearanceEditHe has black hair and eyes and wears glasses. He looks more like his mother than his sisters do.
He is a very quiet and smart person. He mostly keeps to himself and doesn't share his thoughts with others. While he doesn't use his Voice, he speaks through gestures and facial expressions. He's very talented in art, showing him being able to create a cat sculpture out of clay and being able to play the electric guitar. His artistic talent goes as far as to enable him to bend a wooden plank into the shape of a bowl before securing it with nails. He can run fast and has good grades. Some people think he's a furry after making the cat-girl sculpture and dressing up as the faithful dog. He also can spin a pencil really fast to show he is excited.
- Suguru has never spoken throughout the series.
- Main article: Suguru Koshigaya/Image gallery.