A man who initially struggles to cope with a mysterious sleepwalking-crossdressing habit that he develops, worried that it might put his reputation as the school's resident tough guy into question.

Spoiler

As it turns out, he is actually possessed by the ghost of his younger sister, Chii-chan, who initially hijacks his body, before eventually turning into a small beauty mark-like entity. Reina notes that she's not a malicious spirit and there's nothing wrong with a female spirit residing in a male body, prompting the two to coexist as one person with two souls capable of swapping at will, with Tendou researching ways of helping his sister pass on peacefully and occasionally letting her take control.