Senju commands the Senju Liberation Army in a fractured world where Tokyo split into two realms: the sky-bound ruins of Old Tokyo and the grounded remnants of New Tokyo. This division followed a cataclysm that severed all communication and travel between them. As leader of the liberation front, he spearheads resistance efforts against the crisis threatening both cities, coordinating strategic operations to protect citizens from monstrous threats and the looming disaster of Old Tokyo's potential collapse.

He collaborates with key allies—including Touya and Yuuna—while engaging with pivotal figures like Kanata, a New Tokyo youth who awakens a hidden power, and Sora, the enigmatic girl who rescues Kanata and deems him vital to the world’s survival.

In combat, Senju wields specialized forms tailored for distinct roles. His mobility-focused form employs Null Gravity Barrier and Null Block defenses, striking with poison-infused projectiles. His assault-oriented form features Null Damage Wall protection and a unique gauge activating Null Magic Circle and Demihume Slayer enhancements, unleashing Lock-on Piercewave attacks and a Sub Bump Combo that summons a toxic meteor. These capabilities include targeted modifiers against Demihume-type foes, with effectiveness shaped by battlefield conditions and enemy types.