Please Don't Go Anywhere (2017)

なっちゃんはまだ新宿

aka Nacchan wa mada Shinjuku

Highschooler Akino loves her schoolmate Okada, but Okada has a girlfriend called Nacchan. While Akino is busy being jealous of Nacchan to the point of becoming obsessed with her, she realizes that she is more fascinated by Nacchan than Okada.