Papa's Assasin: Daniel wa Tonde Yuku.

High school student Ryunosuke lives with his perpetually popular father, Daniel. Ryunosuke has a secret, which is that he is in love with Daniel. Just as he is overwhelmed by his unrequited love, he meets a good young man, Vis, who looks exactly like Daniel. Ryunosuke begins dating Vis in earnest. However, one day Daniel finds out about their relationship!?

(Source: Taiyo Tosho, translated)