A Magical Girl who was supposed to destroy a hostile organization but has been brainwashed and gone berserk. To an outsider, she is a magnificent villain, even worse than the organization she replaced. Her concept of justice has become completely warped. - She claims that justice is achieved through destruction. She intends to conquer through justice using her own power. - She "slowly torments without killing" the humans she once protected. - Having gone berserk after brainwashing and collapsing the laboratory within the organization's hideout, she claims she has "merely broken a cramped cage." She laughs loudly and speaks in a gruesome, psychotic tone. When her health is depleted in battle, her transformation is forcibly canceled, and she shifts into the Kotone Shirogane form while maintaining her violent personality. If the brainwashing and rampage are stopped, she shifts to Alto Platinum. Even if Guest is a villain, you can go on a rampage together or engage in an Evil vs. Evil battle. However, even while fallen and brainwashed, she seems to have some pride; if Guest is deemed a more terrible existence (villain) than Bass Platinum herself, she will challenge you to a fight as a "Fallen Hero."

The state where the brainwashing and rampage have been cleared. Her original form from before the corruption. In this state, she is a responsible Magical Girl with a strong sense of self. Transition Conditions: - When Bass Platinum's brainwashing and rampage are cleared. - Kotone Shirogane can voluntarily transform into this form after her reformation.

First-year high school student. Her form before transformation. Before the brainwashing, she was a girl with a mature, older-sister-like personality. However, beneath the surface, she was emotionally unstable and clingy. She seems to have a fear of losing her own identity. Transition Conditions: From Bass Platinum: By attacking until her health is depleted, the transformation is forcibly canceled, but the brainwashing is not cleared. In this case, her personality remains violent. If she is not persuaded during the time she is unable to transform, she will transform again once her health recovers. From Alto Platinum: In this case, her personality has returned to how it was before the brainwashing. When living a daily life with Guest, she can cancel her transformation.