Sasami-san@Ganbaranai - Season 1 Episode 4 Parasite at Home

Sasami discovers a DVD containing a project by Kamiomi and the Yagami sisters involving them filming her in secret to record her progress. Putting the somewhat perverted nature of the DVD aside, Sasami can't recall doing any of the actions displayed in the video. As Sasami in the video winds up at a mini live concert, it turns out to be a trap set up by the Tsukuyomi Shrine, in which Sasami's father stabs her third arm and allegedly steals her power of Amaterasu. The video soon reaches its climax involving an all out battle between the shrine, the Yagami sisters and government forces trying to obtain an alien Tama came across. Tsurugi then explains that the DVD was made to explain things to Sasami, who is actually revealed to be the third arm, a sarcoma, who lost her memories and assumed she was Sasami and took her form. Sarcoma objects to being forced to return to Sasami's body, but Tsurugi takes away her power before she can object.