Yahan Rouri is a Japanese college student and roommate of protagonist Asap Suzuki. He launches a politically motivated rocket attack against a US Army camp in Japan, triggering the military pursuit that propels Suzuki into the story's main events. This action arises from his radical opposition to the Japanese government and its American alliance, believing violent revolution is necessary to overthrow the existing power and awaken the populace. His extremist views align with his friend Heiji Kanamoto, though Asap Suzuki understands but rejects their intensity.

Exposure to the alternate world Byston Well grants Rouri the ability to pilot a Shinden-model Aura Battler, a powerful mecha weapon. Gaining this advanced weaponry leads to a significant shift in his character, prompting him to join King Sakomizu's Houjou army forces. This decision constitutes a direct betrayal of his former roommate Asap Suzuki, placing them in opposition during the conflict in Tokyo Bay. His escalating motivations during this conflict include targeting Japanese civilians to achieve his goals, solidifying the rift with Suzuki.

Rouri's narrative arc concludes with his defeat by Asap Suzuki during the climactic battle in Tokyo Bay. The story does not detail his ultimate fate or activities following this defeat, leaving his long-term resolution unspecified.