Hiroki Tsuji is Tetsushi Kaji's best friend and Nina Sakura's boyfriend. He is also the head of the boy's tennis club. 

Tsuji was the one to first introduce Nina to Doraemon and is shown to like Nina more in the manga than the anime. He was the 3rd person to learn that Nina was a witch when he saw Rio (The Cat) turn into a kid into a human. TheUniverseExploded (talk) 20:08, November 4, 2016 (UTC)TheUniverseExploded