when eren asked mikasa what he thought of her, if she said she loved him they would’ve ran away together and spent erens remaining lives with one another. However, mikasa lied and never confessed, so eren never executed that plan bc he thought mikasa didn’t love him like that. Im pretty sure it was an ending eren saw with the founding titan?? he probably gave himself the option to either commit mass murder or live with mikasa where no one would find them. i hope this answers your question

HOW ARE WE GONNA GET A CLOSURE IN THE LAST CHAPTER
btw im confused was the eren-mikasa part a dream or...?