Based strictly on the provided description, Subaru Natsuki is a Japanese teenager originally living as a shut-in NEET, transported to a fantasy world where he encountered the half-elf Emilia and pledged loyalty to her. During this transition, he acquired the "Return by Death" ability, a curse from the Witch Satella that forces him back to a prior save point upon dying, retaining memories of previous timelines. Revealing this curse triggers physical intervention by the Witch's hand, risks killing those informed, and amplifies the "scent of the Witch," attracting hostile entities like demon beasts, undead, Hamsuke, and the Death Knight. Prior to transportation, he struggled with inadequacy and social isolation, exacerbated by an inferiority complex stemming from comparisons to his accomplished father. In *Isekai Quartet 2*, he is transported to a school-based parallel world, serving as a student in Class 2 responsible for Animal Care duties. His appearance remains consistent: a black-and-gray tracksuit with orange accents, spiky black hair, and brown eyes perceived by some as intimidating due to their "sanpaku" appearance. He retains core traits like optimism, bravery, and a strategic mindset but manages emotions more healthily than in his earlier *Re:Zero* self. His devotion to Emilia persists with less obsessive behavior, and he maintains respectful but confused reactions to Rem's affections. He is quick to form alliances, collaborating with Kazuma Satou during the Sports Festival, and demonstrates protective instincts, notably defending Aqua from Tanya's magical aura. His interactions showcase adaptability and moral alignment. He initially distrusts Ainz Ooal Gown due to his skeletal appearance but establishes a tentative friendship after shaking hands, during which Ainz briefly detects Subaru's curse. He shows visible discomfort around Julius Juukulius due to past animosity but cooperates with him during the field day cavalry battle when forming a cross-class alliance against teachers and the Mobile Fortress Destroyer. A rivalry with Kazuma Satou emerges from mutual recognition as former NEETs, souring when Kazuma misinterprets Subaru's life as "surrounded by pretty girls," though they later reconcile. Subaru exhibits impatience with Megumin's antics and dismisses Darkness as a "crazy lady" after misjudging her masochism. Notable abilities carried into *Isekai Quartet 2* include "Return by Death," though Subaru expresses uncertainty about its functionality; he verifies the curse's penalties remain active, including the Witch's scent attracting monsters like Hamsuke. He displays resistance to high-tier magic, notably immunity to Ainz Ooal Gown's Time Stop spell, attributed to his repeated temporal experiences from "Return by Death." His strong willpower, forged through traumatic loops, allows him to withstand intense psychological pressures like Tanya's rage-induced magical aura. During events like the field day, he leverages strategic thinking to coordinate allies against adversaries. His development emphasizes growth from a self-loathing outcast to a resilient protector. In *Re:Zero*, pivotal moments like Rem's unconditional support catalyze his maturity, teaching him to rely on others and confront challenges without despair. This evolution carries into *Isekai Quartet 2*, where he navigates absurd scenarios with humor and determination. The spin-off's non-canonical status means these experiences do not influence his main-story progression. Background elements like Rem's coma after an attack by the Sin Archbishop of Gluttony remain unresolved but motivate his persistent drive to protect allies in any context.