Subaru is a young boy distinguished by his long blond hair, typically secured in a single ponytail. A powerful Collector within Elena Aoki's group, his personality radiates intense pride and a fierce resistance to commands or any perception of weakness. He meets perceived condescension or orders from others with extreme hostility, frequently issuing lethal threats. Elena stands as the sole exception to this defiance; her authority commands his unquestioning obedience, causing him to instantly disregard others' directives when she intervenes. His combat abilities center on summoning and controlling two massive monsters he calls his "Parents." These entities manifest as a merged pair—a male figure on the left and a female on the right—whose limbs function as protective arms, encasing Subaru securely between their palms. This configuration leverages the monsters' immense physical strength for both offense and defense in battle, evoking Norse mythology's Ettin. Subaru's volatility drives key conflicts. Discovering a discarded wallet with Elena and Naoto, he refuses Naoto's order to dispose of it, instead threatening him for perceived disrespect. Later, encountering Shuichi Kagaya and Chihiro Yoshioka—who sought to exploit his separation from the group—he attacks upon sensing their underestimation. His monsters quickly overpower the pair, but Chihiro's unexpected resilience and skill allow her to breach the defenses, damaging one protective "finger." As Subaru prepares further retaliation, Elena's intervention halts the fight. Her command for him to cease using his powers is met with immediate compliance, demonstrating his absolute deference solely to her. His traits and motivations, focused on loyalty to Elena and disdain for disrespect, remain consistent throughout his appearances.