Appearing as a Caster-class Servant in the Babylonia singularity, Musashibō Benkei is summoned by Leonidas I to bolster Uruk's defenses against Demonic Beasts and Lahmu. He manifests with the traditional imposing stature and attire of the historical warrior monk. His capabilities center on defensive magecraft and barrier creation, providing crucial shielding for frontline defenders. Loyal to Uruk's protection and humanity's future, he fights alongside its guardians. A fundamental conflict defines him: he is not the historical Musashibō Benkei. He is a nameless wandering monk spirit whose existence was overwritten upon death by the far more famous Benkei legend. He carries the memories and experiences of Benkei yet knows himself to be an imposter inhabiting that legend. This internal struggle culminates within Solomon's Temple of Time when he encounters the true spirit of Musashibō Benkei, summoned as a Lancer-class Servant. Facing his authentic self forces him to confront the falsehood of his own existence and the weight of the legend he unintentionally usurped. Recognizing the true Benkei's superior strength and resolve, he deliberately provokes the Lancer into striking him down. This sacrifice eliminates the false duplicate, allowing the genuine hero to manifest fully. It serves as his ultimate acceptance of reality and final act of service, enabling the real Benkei to join the fight against Goetia and protect Fujimaru Ritsuka. His story concludes with this act of self-erasure for the greater good.