Hougetsu Shimamura (島村 抱月 Shimamura Hōgetsu) is a high school student. She met Adachi while skipping class on the second floor of the gym in her school when Adachi accidentally walks in on her one day. The two gradually took a liking for each other and began to hang out together all the time. In both manga adaptations, it was Shimamura who walked in on Adachi in the gym when they first met instead of the reverse.
Shimamura has tail-bone length, dyed brown hair, which she keeps out of her face with two clips on the right side. Her eyes are also brown. Despite playing basketball in middle school, Shimamura is on the shorter side. She has a slim figure.
Shimamura finds human relationship as bothersome since she feels that it requires too much effort to maintain such balance. She is conscious of her name being the same of the clothing brand and finds it unpleasant whenever people calls her with her last name. Adachi once said that she had a hard time spelling her name that she would often think of the clothing brand before she could spell her name correctly. She is also a bit of an air-head which Adachi often wonders if she got her trait from her father. She often wonders if taking care of her sister is only a duty that was passed onto her as her "big sister" or simply because she loves her. She also confirmed that she has trouble attaching herself to people but it's different whenever it was Adachi in question. Shimamura has a dog named Gon living in her grandparent's house which they took when she was still young. She stated that Gon reminds her of Adachi sometimes
- Shimamura's zodiac sign is Aries
- Shimamura's natural hair color is Black
- Shimamura's younger sister was called Shimamura Sakura by Adachi in her mind in episode 12 at around 4:00, which has the same name (or only pronunciation, not enough information yet) with Adachi.