電車の中だけしか会わない　私の唇（Chu！）フレンド

Rion, a lesbian student, falls in love at first sight with Yuri, an office worker she only encounters occasionally on the train. One day, seeing Yuri asleep, she secretly kisses her. As the kisses continue, Yuri begins to notice and feels a strange mix of emotions, though their bond remains limited to these train encounters. Once they learn more about each other, they leave the train and their relationship evolves into lesbian intimacy, a story of two women united by their love of kissing.