Hayama Umi

A second-year student just like Wataru. She is Wataru's childhood friend. She is good at cooking and is the one that cooks breakfast, lunch, and dinner for the people who live in the Tsugumi Dormitory. She had a crush for Wataru ever since they were kids, but he seems not to notice.
When Umi was a child, she was very shy. She doesn't like to be alone and she always sticked with Wataru when they were little. She goes almost everywhere with Wataru. Some people dislike Umi and her father because her mother and Wataru's father had an intimate relationship a long time ago.

Edited from Wikipedia