Yuuta Itou's mother, who is suffering from a terminal illness, asks him to film her final moments, and he complies. He records hours of footage, capturing everything from her radiant smile when she is with her family to the times when sickness ravages her body in the hospital. After she passes away, Yuuta compiles her life into a movie to screen at his school. He decides to add a bit of fantasy to the ending of his film, Dead Explosion Mother, featuring a literal explosion! Following the backlash caused by his supposedly tone-deaf portrayal of his mother's death, Yuuta trudges to the hospital roof to take his own life—but there, he meets a girl named Eri. Captivated by his film, Eri requests that Yuuta make a new one that will blow the previous out of the water and prove his critics wrong. The movie they set out to make will stand apart by blurring the line between fact and fiction. And of course, it would not be a Yuuta film if it did not have his personal flavor—just a dash of fantasy.