In Season 1, Subaru is transported to Lugunica, saves Emilia from Elsa Granhiert after multiple deaths, and earns the trust of mansion maids Rem and Ram. After publicly humiliating Emilia during the Royal Selection, Subaru faces devastating loops where Petelgeuse Romanee-Conti and the White Whale slaughter his allies. Encouraged by Rem in Episode 18, he forms an alliance with Crusch and Anastasia, slays the White Whale, and defeats Petelgeuse. However, Ley Batenkaitos (Gluttony) ambushes Rem's convoy, eating her name and memories, leaving her comatose and forgotten by everyone except Subaru.
In Season 2, Subaru and Emilia enter the "Sanctuary" to heal Rem, discovering Roswaal orchestrated every calamity—including hiring Elsa—to force Subaru into sacrificing everything for Emilia per his Gospel script. Subaru undergoes Echidna's Tomb Trials, rejecting her manipulative contract. With help from allies, Emilia completes the trials, while Subaru defeats Roswaal’s scheme, frees Beatrice from her 400-year contract, and destroys the Great Rabbit.
In Seasons 3 & 4, conflict escalates in Watergate City Priestella as the Witch Cult launches an assault led by multiple Sin Archbishops (Regulus, Capella, Sirius, and Gluttony). After defending the city, Subaru’s group journeys to the Pleiades Watchtower. During trial loops set by Reid Astrea and Shaula, Subaru briefly loses his memories, forcing him to confront his own legacy from a fresh perspective.