In Season 1, Yuuki enters Mato and forms a contract with Kyouka, turning the 7th Squad from an overlooked unit into a formidable frontline force. During joint training with the 6th Squad, Yuuki's ability to morph into specialized combat forms under different riders is revealed. The core twist occurs when intelligent humanoid Shuuki attack, led by Yuuki's presumed-dead sister, Aoba. Aoba reveals that human women who consume Mato peaches under traumatic conditions transform into humanoid Shuuki to escape extermination by the upper echelons, exposing dark secrets within the Anti-Demon Corps.
In Season 2, Yuuki operates as a covert bridge between the Anti-Demon Corps and Aoba's faction. The overarching threat escalates when the Eight Gods of Thunder—sentient deity-level entities governing Mato—orchestrate widespread dimensional collapses. At the Commander Summit, Kyouka stakes her career on an offensive campaign against these deities. In the climax, Yuuki undergoes advanced slave transformations through tandem bonding with multiple squad captains, repelling the primary divine vanguard and setting the stage for an ultimate showdown in Mato's deepest cores.