Rapi was once a Mass-produced Nikke with the serial number RR-15436. At some point in time, Rapi met Red Hood, a former member of the legendary Goddess squad. When Red Hood died, Rapi somehow assimilated her entire body, more than doubling her mass and giving her a second core, a feat believed to be impossible. This has given her the ability to release immense heat from her body and intensifying her strength.

Later she was upgraded and became a member of Absolute, Elysion's most powerful squad consisting (currently) of Emma, Eunhwa, and Vesti. However during a mission, one of Rapi's explosives killed a human, causing her to have an identity crisis. This led to Rapi leaving Absolute, much to her teammates dismay, and eventually joining the Counters.