|Height||178 cm (5' 10")|
|Weight||66 kg (146 lbs)|
|Birthday||July 29th, Leo|
|Team|| Kaijō (former)|
Kasamatsu has short, spiky black hair and sharp steel blue eyes. In comparison to the other characters, he has rather thick eyebrows. While playing, he wears the Kaijō uniform with the number 4, as he is the captain. He also wears knee-high socks, and since this is something that no one else does, it makes him unique and easy to spot on court. The socks support his legs and lessen the burden on his muscles.
Kasamatsu is a very responsible and motivated captain. He can successfully lift his teammates' spirits when times on the court gets tough due to how determined, ambitious and strongwilled he is. He uses this motivation to strive towards the goal of winning the Interhigh for his team, because he is the cause of their loss last time. He is also shown to be courageous, as he stopped Aomine by jumping in front of him. He tries his best not to lose his cool during game situations in order not to demotivate his team, and he has successfully led Kaijō to many victories. He is known to be very strict about hierarchy within the team and has the respect of all of his teammates. Though, he can't deal with girls and whenever he talks to one, he ends up blushing and stuttering.
Last year, he and Kaijō High were defeated in the Interhigh preliminaries. This was because when Kaijō was one point ahead, Kasamatsu made a miss pass and let the opponents take the win. He wanted to stop basketball at that time, but Kaijō's coach, Takeuchi, made him captain. He decided that they would win the Interhigh next year, proving his resolve and position as captain.
IntroductionAs Kaijō's captain, he receives admissions from freshmen members at the first practice session. The last one of the first years is Ryōta Kise, who cheerfully introduces himself. Kasamatsu is irritated by Kise's stuck-up attitude and kicks him. Kise is shocked to see the treatment he, a member of the Generation of Miracles, receives, but Kasamatsu opposes by telling him he is still just a freshman. Kise stands up to Kasamatsu, saying that he doesn't care about that hierarchy and that he's better than him anyways. Kasamatsu tells him that before even thinking something like that, he needs to consider the amount of work the second and third years have put into the team.
Seirin vs KaijōKasamatsu appears for the first time on Seirin High's practice match against Kaijō. When the players enter the field, they don't notice Kuroko and Kasamatsu is surprised when he sees him, thinking that he won't such a big deal. The match starts and Kasamatsu dribbles up the ball, saying that they'll start with scoring once. Suddenly, Kuroko steals the ball away from Kasamatsu, passes to Kagami and Kagami dunks, breaking the rim.
Kaijō's coach is convinced to use the whole court and the match restarts. Suddenly, a pack of schoolgirls flock to the court and begin to obsessively scream for Kise, causing him to wave at them. Kasamatsu tells Hyūga that it's always like that, then kicks Kise on the back while scolding him for getting sidetracked. He then tells Kise that they will need to return the favor to Seirin. He passes to Kise, who copies Kagami's move and dunks. The match goes on with a too high pace and Seirin requests a time-out.The match starts again and while Seirin is guarding Kise, Kasamatsu replies with a sudden three-pointer. The match goes on with Kise overpowering Kagami and eventually, Kagami and Kuroko start their co-operation play. Kasamatsu analyzes their play and judges that Hyūga's pretty good too, after he scored some three-pointers as well. He further comments on the progress on the match. At the end of the match, he sees Kise crying over losing for the first time, so he kicks him more gently, then encourages him to prepare for the revenge. When Seirin leaves, he shakes Hyūga's hand and tells him they'll meet again at the Interhigh.
Kasamatsu and the rest of the team successfully make it through the early rounds of the Winter Cup.
Kaijō High faces Fukuda Sōgō Academy in the Winter Cup quarter-finals. Because Kise had to face his former teammate, Haizaki, he asked Kasamatsu to go outside during warm-up for a bit. When both teams line up, Kasamatsu recognizes Hideki Ishida as a national-known player. He wonders why such diligent person would use Haizaki. The match begins and Kasamatsu gets the ball. He sees that Kise is guarded by a tight defending Haizaki and decides to drive inside and pass it to Moriyama, who's free for the three-pointer. Moriyama makes the shot.
The first scheduled semi-finals of the Winter Cup is Shūtoku High vs Rakuzan High, so Kasamatsu and his team are waiting in the locker room. When the match reaches half-time, Kaijō and Seirin hit the court to warm up. The team is later seen watching the second half.
As the match is concluded in Rakuzan's advantage, Kasamatsu is seen warming up for their game next. The match is about to begin and Kasamatsu says to Kise to give them a greeting, at which Kise copies Kagami's lane up and finishes. Kagami returns the favor and both team line up on the court. Kasamatsu and Hyūga exchange a handshake and Kasamatsu notices that he matured into a fine captain, which pleases Kasamatsu. The match finally begins and Kuroko engages a fast assault and scores with his Phantom Shot. It is returned by Kise, who has already entered Perfect Copy. During the next attack, Kasamatsu retrieves a loose ball and passes it directly to Kise, opting for a lightning fast transition. As Kise faces Kagami on the other side of the court, Kasamatsu comments on Kise's use of Akashi's Emperor Eye.
Kaijō has the initiative and Seirin is having trouble scoring. During Kaijō's offense, Kasamatsu fakes a pass to Kise and sends it inside for Hayakawa. His shot is blocked however. Kasamatsu is impressed by Kiyoshi. To slow down the pace, Riko sends Furihata in. Kasamatsu sneers and calls Furihata a terrified brat. Furihata dribbles up court but fumbles the ball and Kasamatsu steals it. Kuroko however, steals it back and asks to go easy on Furihata, as he is a little nervous. Kasamatsu is irked.
He continues to guard Furihata during Seirin's next offense and when seeing Furihata's cautious playing style, Kasamatsu understands Riko's goal by putting Furihata on. Hyūga scores a three pointer and Kasamatsu dribbles the ball up court. He is met by a passionate defending Furihata. He's however no match for Kasamatsu's speed and agility, who passes him with a nifty move. Kuroko suddenly reaches in for a steal, but Kasamatsu spins around and avoids him. He pulls up for a jumper but misses the shot, it is rebounded by Kiyoshi. Kasamatsu later thinks by himself that Furihata is especially good at supporting others and that he avoids danger well.
Apart from his two main attack patterns, Kasamatsu has been noted for his leadership skills, being able to fire his team up in a critical time. He also utilizes his speed for fast and accurate steals. His endurance and passion in the game is fitting for a national-reputed guard.
A chart of his skills were included with his profile in the databook Characters Bible. Kasamatsu's abilities are all nearly perfect, only scoring low on special skill.
Kasamatsu's underclassman. When Kise introduced himself to the team, Kasamatsu saw him as nothing more than a whiny and childish freshman and disliked him as a result. He still often hits him when he's being annoying but they seem to share a strong bond. Kasamatsu acknowledges Kise as the ace of Kaijo, and they share a mutual trust. Kise has somewhat matured since their first encounter, and this probably has a lot to do with Kasamatsu, who beats discipline into him.
Takao admires Kasamatsu for being a strong point guard, and the two seem to have respect for each other.
Kasamatsu and Moriyama are fellow third-years on the Kaijo High basketball team. Moriyama is a close friend of Kasamatsu's and amiable teammate. However, Kasamatsu often gets annoyed by Moriyama's tendency to get distracted by girls, even during serious situations.
- "Buck up everybody! You've tried your best!! We're among the best 8 teams in the whole nation! Go back with pride!" (after their loss against Tōō Academy)
- "I'll tell you what's so great about it. Before you even factor in being good or bad, this is Kaijō High School's Basketball Club. It's not because we were born earlier. The second and third years here have been working hard on this team longer than you have. I'm telling you to have respect for that experience. Doesn't matter if you're from the "Generation of Miracles" or anything else. You're now a freshmen at Kaijō. And I'm a senior here, the captain, Yukio Kasamatsu. Got any complaints?" (his speech towards Kise about the team's hierarchy)
- On the first character poll, Kasamatsu ranked 12th, with 508 votes. He went up to 10th place on the second character poll, this time with 460 votes.He went up to 9th place on the third character poll,with 1451 votes.
- According to CHARACTERS BIBLE:
- He is very bad at dealing with girls. He ends up being nervous and shaking when he tries to speak with one.
- His hobby is music.
- His specialty is playing guitar
- His motto is: "Steady progress; rapid advance."
- His favorite food is Nikujaga.
- His best subject is Mathematics.
- His school committee is the disciplinary committee.
- He has a father, a mother, and two younger brothers.
- His best basketball skills are his drive and 3 pointers.
- He likes girls who are serious.
- On his day off, he goes shopping, buying CDs and clothes.
- He started playing basketball because his parents encouraged him to go to Mini-Basketball.
- In a novel chapter, one of the girls at the little gathering party described his overall appearance as handsome, so he is ironically considered as good looking as well.
- Kasamatsu freezes up when it comes to interacting with girls. All of the girls in his class at Kaijo High take pity on him and only ask yes-or-no questions. 
|Players||Ryōta Kise • Mitsuhiro Hayakawa • Shinya Nakamura|
|Former players||Yukio Kasamatsu • Yoshitaka Moriyama • Kōji Kobori|