Yeong-jae(SinJoo-ah),Ha-eun(KooJi-sung)andChun-hee(YoonChae-i)havebeenfriendsfor15yearssincehighschool.Yeon-jaeistheyoungestofafinehotelownerandsheaimstosleepwith1203menthroughoutherlife.Ontheotherhand,Chun-heeisanold-schoolmindedhighschoolteacherwhohasneverhadsexbeforeinherthirty-somethinglife.WeddingplannerHa-eunwasinlovewithonemanfor10yearsbutrecentlyexperiencedthepainoflosingbothhermanandwork.Thenoneday,tocelebratetheir10thyearmajority,theyhaveapartyoftheirowninroom1203ofYeon-jae'shotel.Theysaythehousebreaksdownifthreegirlsgettogether.Justturningthirty,the3girls'talkgoesoverboard,goingfurtherthanadultrated.Soon,theystartpokingateachother'snervesandendupmakingabet;theyhavetomeetamanandspendahotnightwithhim.TheytargetthehotelbellboyHyeon-soo(LeeYeong-hoon)wholooksjustliketheguyatschoolallthreeofthemusedtolike.Toprovetheirnightwithhim,theymustcollectasampleoftheirsemen.Whoisgoingtospendthehotnightwithhim?Whosleptwiththehotelbellboy?