Finish all other branches, then move on to Mikasa.
Im in the same position.. stuck in a loop 'cause I need to progress each girls branch but it leads back to Mikasa..
Sleep with sister. You have one of the branches unfinished apparently
Progressed a few days and slept with Elsa already, nothings changed..
Check other girl's notes in the journal. It should either say to progress Mikasa's branch or that their branches are finished. If not, do what the journal says.
Ya boi figured it out, it was the creepy ahh mirror man xD
