Ryoma's sister Yuko meets a kind old couple on a bus and strikes up a friendship, visiting them at their assisted living home on the weekends. However, the old man's past as a particle physicist comes back to haunt him. Someone is after his old research for unknown purposes. When Yuko gets caught in the crossfire, the residents of the retirement home spring into action as unlikely heroes to save her. However, will their greatest adventure also be their last?