Kai, possessing powers distinct from those of others, was shielded alongside his frail sister Hikaru by an entity known as ASHURUM. After being recruited by Eiji, Kai was assigned to ASHURUM's special unit, AESES, where he underwent rigorous training. During his free time, Kai would visit Hikaru at the facility's hospital, yet her health never showed signs of recovery. Consequently, a year later, having achieved remarkable progress through his intense regimen, Kai resolves to flee the organization.