One Monday morning on the train, Salaryman asked what Ai did during the Christmas day, but she initially refuses to answer. Later, she reveals that she 'has taken a step into adulthood', moving from 'I-chan' to 'J-chan'.[c]
The anime follows a salaryman who has a chance meeting with a girl named Ai on the train. They begin to meet every Monday on the train, with the man serving as her bodyguard on the crowded commute while they chat.