Birthday: November 12

The male lead of the series. He had no goal in his life, because he was too smart to find one. He is considered very cold hearted and is considered as the smartest person in Japan having an IQ of 200 and always being number 1 in all exams. He is also a very good cook and an excellent tennis player.

The eventual husband of Kotoko. Later, because of Kotoko's encouragement and advice, he decides to become a doctor. In volume 7, Kotoko was asleep under a tree and Naoki kissed her, which was seen by Yuuki who realised that Naoki does, in fact, love Kotoko. In volume 10 during tennis practice, when he heard from Zinko and Satomi that Kinnosuke proposed to Kotoko and that she is going to answer him on that day, he left looking upset and waited for her in the rain. They had an intense and emotional (mostly Kotoko; Naoki looked calm all throughout) conversation - wherein he said to Kotoko not to love anyone else but him. He hurriedly went home with her and asked her father to give Kotoko's hand in marriage to him to everyone's shock. That same night, when Kotoko asked him if he's sure about what he's doing, he assured her and told her that he really does want to marry her. In volume 19, during their marriage, when he was having a heart-to-heart talk with Kotoko's father, he said that Kotoko has no idea how much he loves her.