Every Monday morning during their train commute, Oniisan, a typical salaryman, dutifully shields high school student Ai-chan from gropers. As their encounters become shorter, their connection deepens, giving them valuable glimpses into one another's lives. Ai-chan shows her backing by presenting Oniisan with small mementos to ease his Monday blues. Ai-chan and her captivating circle of friends spread happiness among their male buddies and colleagues, enlivening the onset of the week and providing encouragement for the days to come.