Tsuma no imôto: Abunai chôhatsu (2013)

Machiko, a nurse, married Norio, a businessman with a fetish for cosplay. After their marriage, the couple's life together continues to be active, and they partake in each other's company every night. One day, Norio discovers Fumiko, Machiko's sister-in-law, in a sailor costume in one of her photo albums, and they have an affair with her in their fantasy. Also, as soon as Machiko returns home to her parents with the news of her former teacher's death, Fumiko shows up at the wrong time. Norio's exciting life begins when his cute sister-in-law shows up while his wife is away..