An Impure Physical Relationship That Began When Her Best Friend Confessed To Her. A Double Affair Flares Up, And The First Time They Have Nakadashi Sex Feels So Good That They Fuck Each Other For A Few Days Of Backstabbing Cohabitation. Ruu Tosoku

Ken and Mai, along with Ruu and Jun, are two couples who get along well. One day when Mai is away, Ken and Ruu are drinking together when a tipsy Ruu suddenly confesses to Ken, 'I've actually always liked you.' Though hesitant, Ken is swept up by Ruu's momentum and they end up having a physical relationship. Over the next few days while Mai is away, a brief cohabitation between Ken and Ruu begins.