Can’t you see the reason? Her memories with her grandma was there. Of course she’d think about her grandma.
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
i like how you belittle her grandma's death by saying yuki's memories of her aren't as important as the mood.
Go on a romantic onsen trip with your boyfriend....and all you can think about is your grandma.
Way to kill the mood........