"Is a person like me allowed to love somebody?"
|Relatives||Koharu Hoshizuki (Elder Sister)|
|Anime||Episode 8: Aries Part 2|
Kotarou has long turquoise hair and light violet-coloured eyes. He has a small piece of hair hanging down. He wears a white typical scientist jacket over a v-collared shirt. He also has a purple scarf around his neck and wears apple-green jeans.
Kotarou represents the Libra. He is prone to feeling sleepy and is quite disorganized, often creating a mess that Tsukiko Yahisa cleans up. He is the school nurse who had ambitions to become a doctor. In games other than In Autumn, he is often absent from the nurse's office when he is needed. When he was in middle school, Kotarou's parents took in Iku Mizushima and Yui Mizushima. They had a very strong and sibling-like bond. Because of Yui's illness, Kotarou aspired to become a doctor and cure her. However, Yui had romantic feelings for him and after her death, Kotarou blamed himself for not being able to save her. He feels that he doesn't deserve to love anyone because of this. He also lost his motivation to become a doctor and instead, became a school nurse. He does not take his job seriously and often naps or leaves the infirmary while still on the job.
His father is the chairman of the academy, but after his father's retirement, the position was given to Kotarou's sister, Koharu Hoshizuki. However, he ended up obtaining the position due to Koharu's wish to work overseas. Despite his new title as chairman, he remains the school nurse. He is weak to liquor and will pass out after ingesting some. He also dislikes computers and asks Naoshi Haruki to handle all computer-related work.