Arisa arrives at Seven Arts as a new idol. However, she is immediately scheduled to appear in the Underground Idol Lewd Sports Festival. Not knowing anything, Ibuki struggles and puts her body on the line to protect her junior, Arisa, but ends up being fucked in various competitions. Koharu, from the idol unit, mocks her while engaging with Kurozuka... And then she learns the truth about Arisa, whom she protected with her body...!