im looking for this tragedy yaoi manhwa

I read this a long long long long time ago I vaguely remember it

A boy loves his father of course the boy was adopted. The adopted boy wanted to become a teacher to follow his not real father’s steps. The son(adopted) loves his father so much that he wants to have sex. I think they did. But here is the plot twist (I think)
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The adopted boy was the one who killed his father’s biological son and the reason his father adopted him was to kill him, but he didnt, in the end the father killed himself infront of his adopted son