I think the black haired guy (The one who left first is the father) ...We know every plot twists in BL/Yaoi is on another level. He might've left first. Then the three get drunk right. Then so when the three got drunk, The black haired guy might have come back to the Uke and do "It". My theory isn't great but at the first chapter, The black haired guy is clearly the father in my perspective. It's obvious com' on.
I think the black haired guy (The one who left first is the father) ...We know every plot twists in BL/Yaoi is on another level. He might've left first. Then the three get drunk right. Then so when the three got drunk, The black haired guy might have come back to the Uke and do "It". My theory isn't great but at the first chapter, The black haired guy is clearly the father in my perspective. It's obvious com' on.