Kazuya is a cowardly bitch, the likes of which curses world literature once every solar eclipse. He is not going to confess. Mizuhara, understandably, can't think of anything right now. Here are the options:
1) Granma dies. It will deprive the readership of a good simpathetic character, MC will do some romantic speech, will interrupt himself at the end saying the words "HOLD ON BUT NOT IN A WEIRD SENSE", or similar phrases, Mizuhara will smile and laugh and then they watch the movie and they cry a lot. End. Granma will be forgotten in like the next arc when Kazuya will be too busy trying not too stare at Rika's breasts or something.
2) Granma lives. Big Cry. Cheesy romantic "but not like that" dialogue can still be had right before she recovers. She watches the film. Big Cry again. End of the arc.
3) Granma dies and Kazuya decides to stop fucking around with the girls' emotions. AHAHAHAHAH YEAH RIGHT FELLAS, can you imagine Character Growth? Ahaha what's that, can you eat it? LOL.