Kohinata Umi

A quiet and serious Kouhai who always has a smiling face.
She stands up for the people around her, and always takes that role of a follower.
She is very adaptable and is able to keep up with the protagonist's dirty talk and the bad moods of her classmates.
She lives near the MC and often go to school together, including Miya,
Since she is the youngest of the student council, she is treated like a younger sister, and she sees the protagonist as an interesting senpai.