geonpil was selfish cuz if u remember his backflash, he literally had noone to rely on other than himself up until he met yeonseung who unfortunately had romantic feelings for geonpil.
yeonseungs constant love for geonpil being the only flaw to his character seems minor in comparison but its a killing flaw and thats why yeonseung doesnt deserve to get treated like he didnt do anything wrong, he practically signed his own death letter by choosing to ignore the fact that he knows geonpil is acting oblivious to his feelings on purpose, years of living in such an environment would erode anyone
but why would you say geonpil dgaf about yeonseungs death hello?? did you not see the 10+ chapters of geonpil literally going crazy?

i'd rather for that fuckass demon and hyung to get together than for geonpil to have a good ending