Kai has jet black hair shaved into a buzzcut, somewhat thick eyebrows, and full lips. His eyes are heavy lidded, giving him a relaxed and approachable appearance. Whenever shown, he's usually beside Yaku or not too far behind him. He wears the jersey number 2.
Kai is a calm, collected, and peaceful person who is mostly in the background, giving him the role as Nekoma's vice captain. He doesn't talk much, but when he does, he's always polite. He's a very calm person in general.
Kai joined the Nekoma volleyball club in his first year, along with Yaku and Kuroo. He is shown to have put up with their squabbling, and when the first years were asked to state their goals in the club, he went along with what they said, which was to dominate nationals.
Karasuno High Team Formation ArcEdit
Kai is introduced along with the rest of the Nekoma volleyball club during the practice match with Karasuno. During the match, he appears to face off with Daichi in being solid receivers but the two seem to become friends after the match.
Tokyo Expedition ArcEdit
Kai mostly appears during the practice matches.
Spring High Preliminary ArcEdit
Nekoma vs. FukurōdaniEdit
Kai participates in the match between Nekoma and Fukurōdani.
Nekoma vs. NohebiEdit
Kai plays with Nekoma against Nohebi. When Yaku injures his ankle, Kai is shown being concerned but follows Kuroo's lead that they should continue to push through and do everything they can to win the last spot to represent Tokyo for the Spring Tournament.
Tokyo Nationals ArcEdit
Nekoma vs. KiyokawaEdit
Kai is seen being able to get solid receives against Kiyokawa's ace.
Nekoma vs. SarukawaEdit
With the rest of the team, Kai tries to help protect Kenma from Sarukawa's attempts to bring down the Nekoma setter. He follows Kenma's instructions on which receives would be best for the sets he needs and is seen landing a few spikes throughout the second set. When Nekoma wins the game, Kai celebrates along with his teammates.
Nekoma vs. KarasunoEdit
Kai's final appearance of the series is when he reunites with his former teammates at Kenma's house. After high school, Kai became a gardener and arborist.
Not much of his abilities have been shown so far, but Kai appears to be a stable player like the rest of the team. He is flexible and very good at receiving.
Jumping Reach: 309 cm
He has a good relationship with his teammates and gets along with everyone, especially Kuroo and Yaku.
Kai became fast friends with the two during their first years. They joined the volleyball club together and were often with one another, though Yaku and Kuroo would argue with each other all the time.
- Favorite Food: Sea grapes
- Current Concern: He does have some trivial concerns, but he figures that as long as you're alive, things will work themselves out one way or another.
- His star sign is Aries.
- In Haikyuu's first popularity poll, Kai placed 34th with 324 votes. He did not rank in the second poll.
- Nobuyuki (信行)
- 信 - Trust
- 行 - Go
- Kai (海) - Sea
- Nobuyuki (信行)
- "Have you guys already decided you're joining the volleyball club? If so, I look forward to working with the two of you for the next three years." (to Yaku and Kuroo, Chapter 200)
- ""There's not many people out there who'd believe 100% that they're the ones to win." Maybe "belief' isn't quite the right word here. There are people who are crazy about victory. (Chapter 327)