Notes:

I'm glad I'm finally done with this. At first, when I finished the Worst Food reactions, the Hot Springs reactions never crossed my mind. However, when I discovered that the Head Towel accessory guarantees that character would show up in the Hot Springs, I decided to go through and gather every character's reaction when you walk in on them in the baths.

Now, the Head Towel does not always guarantee the character you want in the baths to show up. If you're trying to get Felicia, Jakob, Flora, or Gunter to appear, they can't be the assistant of your Castle otherwise someone else will appear. Another thing is if your spouse is part of the group bathing together, then it will just be you and your spouse. Your spouse won't be bothered by you showing up and you're just going to have to go through another skirmish or My Castle battle until another group shows up.

To get your own Head Towels, you need 20 daikons and a Level 3 Accessory shop.

This group set makes up the neutrals, the royal siblings, and Anna.

The individual reactions of everyone else are here.