I don't see a trist with a married friend causing the kind of rift that transpired between He and her sister. The explanation is a straw hat to evade the truth as the event was really traumatic. Far beyond what an adulterous relationship would have caused, this severed all contact for years. JMO.Was it that? I thought the sister caught him with someone a married friend of hers or something? it's been so long since I played it but I don't think anything has happened between the MC and the sister.