Cross Method in the Dead of Night

Hiroki has a NEET Shut-in for an older sister, which leads him to always think "It's better to be a girl!"
While taking care of his lazy self-centered sister Yui, he has finally had enough of her behaviour, and snaps at her. Griping about his sister, Hiroki mutters "I wish we weren't related", and accesses a mysterious website address.
The website claims to allow you to enter the body of another person, as long as you are willing to make your own body available as well. Skeptical, Hiroki tries the service and winds up in the body of popular idol Mikuriya Mikuni.
While spending time as Mikuni, Hiroki is involved in finding out a secret about her he'd rather not. At the same time, when seeking to go back to his own body, the person occupying it tells him something outrageous has just happened!
What happened to Hiroki's body during the incident? And what is the idol Mikuni's big secret? Be witness to the suspense as these mysteries pile up!