High-school student Ai crashes into a burned-out salaryman on a packed morning train, and the two start meeting every Monday as he shields her from the crowd on her commute. Their quiet, once-a-week routine grows into something more as the manga widens out to other mismatched pairs, including college freshman Maegami-chan and her former high school teacher. Each chapter stays a short, single-scene vignette built around the same weekly commuter-train setup.