Watashi ga Kieru is a social mystery about Fujimaki, a former detective who learns that he has symptoms of mild cognitive impairment and investigates the identity of an unnamed elderly man known as Monzen-san at a care facility. Asked by his daughter for help, Fujimaki begins an inquiry within his remaining time and approaches a truth hidden in the man's past.

As his own memory begins to falter, Fujimaki traces the past of a nameless old man in what may be his final investigation.