Sewashi Nobi is the great-great-grandson of Nobita Nobi and Shizuka Minamoto, originating from the 22nd century. His physical appearance mirrors Nobita's son Nobisuke, characterized by fair skin, black hair, and large black eyes, though his hair appears ginger in the film *Stand by Me Doraemon*. Early anime portrayals featured him wearing glasses and a red jumpsuit; later designs removed the glasses and updated his attire to teal and white shirts with boots or jumpsuits. Journeying from the future to Nobita's timeline with the robotic cat Doraemon, Sewashi aims to alter his family's disastrous destiny. Nobita's chronic failures lead to bankruptcy, immense debt, and marriage to Jaiko, creating generational hardship. To rectify this future, Sewashi tasks Doraemon with guiding Nobita towards lasting happiness, installing an "accomplishment program" that prevents Doraemon's return until Nobita succeeds. Personality-wise, Sewashi shares Nobita's academic challenges but displays greater athleticism, confidence, and technological aptitude. He is energetic and proactive, though he similarly fears dentists. His actions prioritize family welfare over personal attachment to Nobita, employing pragmatic use of future technology by equipping Doraemon with helpful gadgets. Sewashi presents Nobita with a photo album depicting an improved future where Nobita marries Shizuka. Some fans speculate this album could be fabricated, as altering the past risks paradoxes; images remain unchanged despite timeline shifts, suggesting Sewashi's actions might form a predestined causal loop rather than altering history. Sewashi asserts his existence is secure due to Doraemon's interference ensuring his birth, though this remains ambiguous. His family includes his mother, depicted once with a futuristic resemblance to Nobita's mother, and his father, Nobita and Shizuka's great-grandson, who appears briefly in spin-offs like *2112: The Birth of Doraemon*. Nobisuke is confirmed as Sewashi's great-grandfather. In *Stand by Me Doraemon*, Sewashi plays a pivotal yet brief role: after delivering Doraemon and explaining the mission, he returns to his time, directly initiating the film's events including Nobita and Shizuka's marriage and Doraemon's temporary departure. Sewashi's timeline origin varies: the 1973 anime places him in the 21st century as Nobita's son or grandson, while later versions consistently designate the 22nd century. Some international dubs, like the Indian version, inaccurately identify him as Nobita's grandson. His character lacks significant development across media, remaining confined to initiating Doraemon's mission with consistent motivations centered on familial duty and technological intervention to break the cycle of debt.