Sankaku (さんかく) (Triangle) is a 2010 Japanese film directed by Keisuke Yoshida.

He is oddly bothered by the sound of Momo going to the toilet in the middle of the night, she wanders around in her loungewear that is practically her underwear, and she cutely whispers things to him, and he spends his days feeling uneasy since Momo's arrival.

Furthermore, that night, Momose can't sleep and goes to the bathroom, and when Momo wakes up, they naturally kiss.

Meanwhile, Momose, driven by the urge to see Momo, drives to her father's house where Kayo lives, too.

Early in the morning, while Momose is waiting in the car near Kayo's father's house, Momo appears on her boyfriend's bicycle, with him riding with her.

Seeing Kayo looking surprised and suspicious, Momose crouches down and repeatedly laments his own foolishness.