First Love Monster (2016)

Fifteen-year-old Kaho Nikaidou is ready to leave her sheltered upbringing behind as she begins a new chapter in a Tokyo high school dorm. However, her adventure takes an unexpected turn when a truck nearly collides with her! Just in time, a charming stranger saves her, and Kaho quickly finds herself infatuated with him. After a determined search, she confesses her feelings, only to discover that her savior, Kanade, is actually the son of her landlord! While he agrees to date her, Kaho's happiness is short-lived when she learns that her boyfriend is just a fifth-grader!