Hiroki Tsujiai  

, 辻合 宏基

Tsujiai, also known as Kaji's classmate Ayu and Nina, is the leader of the male tennis club and has a flamboyant personality. Despite this, Ayu seems to dislike him because he often interferes with her relationship with Kaji. However, Tsujiai introduces Nina to Doraemon, who becomes one of her favorite characters. His best friend is Kaji, and while the anime doesn't show it as much, the manga suggests that he has feelings for Nina. He also owns a cat named Shinnosuke and was the third person to learn about Nina's secret identity as a magic girl after witnessing Rio transform into a human.