Gender | Male
Birthyear | Wayward 6
Specialty | Flamberge, Kris Knives
Position | First Mate
Sei has been with Hyouki since before the creation of the crew, and was a servant of the young prince before that. He is ambidextrous and switches his weapon from hand to hand during fights.
- Sei has a row of earrings on his left ear, matching Tenrou's
- Sei's name means "green" in Chinese and "blue" in Japanese
- Sei has a cross-shaped scar on the left side of his face