Movie
Description
Yu Ninomiya, known as Yu, survived an infant plane crash that killed his parents but caused permanent paralysis requiring a wheelchair. Raised initially in a Tokyo hospital, he met an elderly patient sharing tales of magic and travel between worlds. Later adopted by a florist, he lived with his adoptive sister Saki Mishima. During childhood, he intervened when a dog attacked his future friend Haruto Ichihara, drawing the animal towards himself so both could escape, forging a lasting bond.

In high school, Yu applied his sharp intellect to develop basketball strategies for Haruto, a star athlete. Both developed feelings for classmate Kotona Takashina, though Haruto ultimately dated her. Yu sometimes missed group activities due to inaccessible locations. When Kotona called in distress, Yu located her being pursued; an assailant stabbed her with a mystical dagger just before Haruto arrived. Fleeing the scene, all three narrowly avoided traffic and were transported to Ni no Kuni, a parallel world where Yu could walk.

There, Yu and Haruto encountered Princess Astrid of Evermore, who resembled Kotona and bore identical curse marks. Yu removed a manifested dagger from Astrid's chest, breaking her curse. He deduced a life-link between Kotona and Astrid across the worlds. After Kotona was diagnosed with a terminal brain tumor in their original world, Haruto resolved to kill Astrid to save Kotona. Yu opposed this plan, refusing to sacrifice Astrid.

Captured in Ni no Kuni during another assassin encounter, Yu was forced into a duel against Haruto during the Black Banner army's invasion of Evermore. Their near-fatal clash returned them to their original world. Yu inferred that Saki's life was linked to the captured knight Bertha Roam and collaborated with Haruto to rescue Saki from the assassin, who transformed into a monstrous entity. Returning to Ni no Kuni, they exposed Crown Prince Sedulus Astrum as the true antagonist manipulating events while disguised as the king's advisor.

During the final confrontation, Yu intercepted Sedulus's lethal strike aimed at Astrid, sustaining critical injuries. An elderly man revealed as Oliver from another timeline declared Yu a hero. Empowered by the Divine Avnaron and wielding the sword Mornstar, Yu helped defeat Sedulus before passing Mornstar to Haruto for the killing blow. The resolution unveiled Yu's origin from Ni no Kuni, not the human world—his presence during Haruto's childhood was a temporary crossover to save Haruto from the dog attack. Post-battle, Yu chose to remain in Ni no Kuni as Prince of Evermore, entering a relationship with Astrid. Those in the human world forgot him, though Haruto retained their shared memories.

Yu consistently demonstrated strategic thinking, loyalty, and moral conviction, contrasting with Haruto's impulsiveness. His journey transitioned him from a reserved student constrained by disability to a decisive leader embracing his true heritage. In Ni no Kuni, he exhibited enhanced combat skills, tactical prowess, and the ability to wield bluish magic during battles, notably against Haru and Galeroth. His abilities included expert swordsmanship and tactical acumen, vital in battles like the Evermore Colosseum and the defense against the Black Banner army. His connection to Ni no Kuni enabled him to utilize Mornstar effectively during the final confrontation.