Responses
Wouldn't make much difference in the end. The sidestory Paradise seems to have strongly suggested they would have broken up either way. Seju had too much baggage with her toxic family involved and Sumin isn't strong enough to handle that.
i am left wondering what could've happened if seju didn't cheat? would they be happy? would she and sumin be happy in the future? they looked so happy back then that you'd be left wondering what went so wrong