It still has never made any attempt at explaining why he, Geon Woo, pretended to not know the MC. In chapter 2, Geon Woo is asked if he has any childhood friends, and he flat out says no.
I felt like this scene, where he shows jealousy that Hana enjoys talking to the blond guy, Seju, kind of sort of elaborated on that? But not really? That flashback must have been to before the MC and Geon Woo started "dating", but wouldn't that also be when he was pretending not to know her?
Or is the implication supposed to be that he got so jealous that he pretended not to know her because of this?