|Manga||A Good Catch|
|OVA||The Obstacle Course Swim Meet|
|Japanese VA||Yamaguchi Kappei|
Kousuke is Ataru and Hokuto's best friend and the three of them are often seen causing trouble together. He has a girlfriend (who was willing to pose as Kumino Otoko for him), and has received Valentine's Day chocolate from other girls, meaning he is somehow popular with girls. Like Mendou Shuutarou and the other male students, he is also in love with Lum and will try to prevent her from kissing Ataru, trying to protect her purity. In the later half of the series, he and Hokuto begin to become victims of the daily shenanigans. In the anime he only ever appears as a background character, and his roles are always given to either Megane or Perm.
He and Hokuto appear in the first chapter of the manga, but are replaced by Lum's Stormtroopers in Chapter 3. Kousuke reappears shortly after Mendou debuts and quickly claims the position of main supporting character. In the anime, a lot of his major roles are taken by Megane, such as the Kumino Otoko plot and receiving a love letter from Lum in "Capture the Heart". In the final scene of Urusei Yatsura: Final Chapter, Perm watches on in Kousuke's place when Lum and Ataru embrace.
His handwriting is messy and he has poor writing skills, which Mendou frequently insults him for. However, his writing skills are good enough to trick Ataru in the Kumino Otoko story.