A woman named Ayumi Natsukawa, known for her promiscuous past during college days, has changed significantly since becoming a working professional. She has been devoted exclusively to her husband, Takeru, for seven years after they married last year on their first wedding anniversary. They decided to take their honeymoon at a local hot spring town where she had reunited with some old classmates from university. Upon meeting them again, Ayumi realized that these people were part of a group called Yarisas (sexual enthusiasts) which included herself when she was still a student. Determined not to fall back into her old ways, Ayumi vowed never to succumb to their influence. However, as memories of her wild past resurfaced, she found herself slowly losing control...

経験人数50人。性に奔放だった学生時代とは打って変わって、社会人になってからは彼一筋の夏川あゆみ。会社の上司である真面目な彼と7年付き合って去年ついに結婚。結婚1年記念旅行としてやってきた地元の温泉街で大学時代の同級生と出会う。「こんな奴らと二度と会いたくなかった…」彼らはあゆみが所属していたヤリサー仲間だった。なんとしても彼らになびかないと誓い、決して自分を見失わない強い意志を持ったあゆみだったが昔の思い出が徐々に蘇っていき堕ちていく…。