GUYS I JUST REALIZED. Sung Il-Hwan, the super strong guy that came out the A-rank gate in the US, must be Sung Jin-Woo's father!! He must have gone missing in that dungeon and that's why the MC takes care of his sister alone!!
I think the webtoon made it obvious enough for readers to get the same thing ^^;
GUYS I JUST REALIZED. Sung Il-Hwan, the super strong guy that came out the A-rank gate in the US, must be Sung Jin-Woo's father!! He must have gone missing in that dungeon and that's why the MC takes care of his sister alone!!