It's not an isekai..it's a soul switching type of manhwa where the MC who has led a miserable life is inflicted with a life threatening disease, then she is visited by a spoiled noble lady who is suicidal talking on and on about how she envies her (that she will meet her end soon). So what did she do? She made a deal with a witch to switch their bodies so she can fulfill that suicidal girl's wish..so that girl dead now. She now possess that lady's body, then discovers what made her suicidal. The lass led a colourful life. Her butler gave her head and made her reach climax on the first day. Then her fiancee came with his friend, that friend later like sexually assaulted her in front of him which he is turned on by. He is a cock block right? Is that the term for it? He becomes rock hard witnessing this scene, the line " Your fair body is being violated by *insert friend's name* tanned and muscular body. It is such a beautiful sight"..while eating dessert mind you. So we later find out that the friend likes her which she confirms by going into a secret store he owns, buying a potent drink to end her life which then he chases her for and takes it away from her all the while doing some sexy thingsss...the MC dresses a bit vulgarly, throwing away the former lass' dresses to be replaced by dresses with a low back and chest showing attire. There is also like a bit of revenge plot line going on..but whatever. It is a smut. I don't enjoy it like 'Ch** chan k******* n*kk*' but it is alright..
Concentration of Malice