Nobita Nobi, the academically challenged and physically uncoordinated elementary school student, drives the plot of "Doraemon: What Am I for Momotaro" when his curiosity about a historical photograph resembling the Momotaro legend triggers a time travel investigation with Doraemon and friends. During the adventure in feudal Japan, Nobita clumsily falls overboard while boarding Doraemon's Peach Submarine, requiring him to remove his wet clothes inside the vessel. Separated from the group, his submarine is found by an elderly couple who perceive him emerging from a giant peach, positioning him as the Momotaro figure. Suneo, Gian, and Shizuka consume Animal Transformation Biscuits, becoming a dog, an ape, and a pheasant respectively. They rendezvous with Nobita, solidifying their roles as Momotaro's animal companions. The investigation reveals the feared "oni" on Demon Island is actually a stranded Dutch sailor forced to masquerade as a demon for survival. Nobita exhibits compassion for the sailor's predicament. The gang's inadvertent actions in the past create the Momotaro myth itself: Nobita becomes the legendary Momotaro, his friends inspire the animal companions, and the Dutch sailor's fabricated oni persona forms the myth's antagonist. The photograph that sparked their investigation is confirmed to depict Nobita as Momotaro with his transformed friends, creating a closed temporal loop. The Dutch scholar researching this photograph in Nobita's time is revealed as a descendant of the encountered sailor, establishing an Identical Grandson connection. Nobita's participation resolves the historical mystery, demonstrating his occasional capacity for unintentional heroism through compassion.