Ryusei is a 16 year old boy in Mahiru's class. He has blonde hair held back by a red headband. His eyes are gray. Ryusei's wears an orange blazer with a white undershirt and a dark blue one. The clothing is worn loosely and unbuttoned. Ryusei wears light brown pants and white and blue shoes.
Ryusei is first seen with Mahiru in class preparing for the cultural festival with Koyuki and Sakuya.
When the four of them are stopped on the street by Berkia, who is posing as a magician, Ryusei remarks that magic is lame and tries to leave. Berkia stops him from going and asks the others a question. He asks them why he stopped Ryusei, then gives them four multiple choice answers for them to choose from- all of which are correct. The choices were:
- He ignored me.
- Walked past me.
- I'm hungry!
- He ignored me. Again.
After announcing that all answers are true, Berkia bites into Ryusei's left shoulder/neck and lets him fall to the ground. Koyuki then takes Ryusei into his arms and shouts for help.
The next day at school, Mahiru rushes in, concerned for Ryusei. He finds Ryusei with a bandage around his neck and Koyuki tells him that Ryusei was in an accident. Confused, Mahiru reminds them of what happened the day before. The two don't believe him and say that he is telling one of Sakuya's fairytales. Ryusei tells Mahiru that he wasn't there when he was injured.
- He is a little shorter than Mahiru and Koyuki.
- He is the first character (following the storyline) to be bitten by a vampire.
- He plays soccer at the national level.