Go on a romantic onsen trip with your boyfriend....and all you can think about is your grandma.
Way to kill the mood........
But that part was important though.....if you think about it, it adds to yuki's character development; as when she is a kid she actually wanted to come alone with her grandma but says th she didnt want to be selfish or cause problems.....this smoothly leads into her sayin she wants to come alone with naruse next time which is a big step for yuki as she is starting to be more honest with herself
Theory: Uke goes crazy....locks up seme so that he cant leave..while hysterically proclaiming that he'll die..and "i do this because I love you. I'll save you"
But....he dies still.
I feel like I know this plot from Amnesia