Nazeka?!  Sweet Home

 なぜか？！ すぃ～とほ～む

Kazuya starts living at his brother's house. His brother, Tatsuya, is busy with working and always comes home late. Kazuya gradually gets close to Tatsuya's wife, Minami. As a result, Kazuya sleeps with Minami.... But it is Tatsuya's trap. He wants Kazuya to lose virginity early. And one day, Miyuki, Minami's mother, comes to his house and it does not take long before Kazuya has sex with Miyuki.... Also, his aunt, Kasumi, joins them....