After pursuing Yuu again and again before finally marrying her, I thought our happy life was secure—until my junior coworker Koichi changed everything. During lunch, he boasts that married women are the easiest to seduce and claims he could win over Yuu too. Furious, I challenge him to try. Days later, I invite Koichi home and make an excuse to leave him alone with my wife for three hours. When I rush back, I completely believe them when they insist nothing happened.