Kou Miete Haetemasu.

"She has a secret." "It's a secret that only I know.." My childhood friend Yuika is a girl with long black hair, good looks, and she's popular with the other students. Today, a boy confessed his feelings for her. But she won't go out with anyone. No, she can't exactly go out with anyone. Because of that "thing" growing on her.. That "thing" made Yuika's life more difficult with each passing day. It seemed hard for her to live constantly worrying about the people around her. But that was in the past. Yuika and I had a secret routine that freed her from "it." This is the story of how that secret routine began. I'm the only one who knows about "it" as a secret. I'm the only one who can set Yuika free. (Source: DLsite)