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Chowon actually kipnapped and had Heesoo raped. He failed only because he was stopped. His place is in the prison. Or at the very least a mental institution. Though mental illness does not excuse what he did. Making reader take pity on him out of his mental state is an insult to all people with mental issues out there who try to have healthy happy lives. They do not hurt other, and blame it on mental issue.
This manga is not necessarily a realistic description of a DS relationship. But compared to other "BDSM" yaoi, which are mere fangirl fantasy, it is certainly better. Author has done some research at least.