The memory-locking ability, while potent, has unintended side effects that drive the episode's second half:
Origami also undergoes a personality shift back to her "new timeline" persona, which remains unaffected by the memory seal. The "Kiss Contest" Date
The episode begins with the aftermath of Shido's date with Mukuro. In a shocking turn, Shido discovers that his friends, including his sister Kotori and the other Spirits, have completely forgotten his existence. This is revealed to be the work of Mukuro’s Angel, , which she used to "lock" the memories of everyone close to him. Her goal is simple but extreme: to ensure Shido belongs only to her, free from the "clutter" of his other relationships. The Return of Inverse Personas