Imma guess that both of the cursed kids are not gonna drink the miracle potion so they can be together. Or the boy gave it willingly to the Galfa's kid. They currently can only make one, no?
Imma bet a single strand of hair from my left nut that Old Man is the LN Haruka, and the manga is another timeline where he did not do sexual shit that got him and the gang into trouble or some world ending shit