 He explains that the walnut-shaped object is a time-traveling device, and he used it to leap through time hoping to see a painting that is being restored by Kazuko, as it has been destroyed in the future.While walking with Makoto in the frozen city, Chiaki also explains why he stayed longer in her time frame than he originally planned.Consequently, he has used his final leap to ensure Kōsuke's existence and has stopped time only to explain to Makoto now that he is unable to return to his own time period, and having revealed his origins and the nature of the item that allowed Makoto to leap through time, Chiaki must leave.