
sorry but no one and everyone is at fault in my eyes. ML was upfront about the situation but also wrong for accepting and committing infidelity during the marriage. Sister was blinded by love but wrong for getting mad at the exact situation the ML warned her about. MC was stuck in a sticky situation but was wrong for keeping quiet about his past relationship with the ML.
idk why you people are solely blaming the sister when each one of them are at fault. yeah the sister knew, but she had a reason for being stupid. the same way the MC had a reason for not being able to tell the sister what was going on between him and the ML before and during the marriage lol.
the point of this situation was that each one of them is wrong, hope this helps!
R18 Given ahh plot