Where would you take Mishima out for a date?
I'm 10 years his senior, so I wouldn't.
In my fics, though, he and Akira have gone to
The planetarium for a proper date
Out to eat for ramen and ended at a dessert shop
To Destinyland with all the Thieves
A crepe stand (Akira eats them to indulge Mishima, he typically gets the savory ones)
The aquarium and the hotel buffet (this doubled as an event for Mishima's birthday)
A small diner before visiting a bookstore Mishima likes
The beach as part of a roadtrip during college break
Akira's dorm so he can give Mishina cooking lessons
Mishima's dorm so they can talk about the book; instead they end up cuddling
Leblanc for a study date, though one occurrence was before they were dating
I believe that's all of the "proper" dates. I've written a lotta shuyuu. I will continue to write a lotta shuyuu
If we're talking canon compliance / where I think the game would let the protag take Mishima on a date, I'd pick the Aquarium and Destinyland, since you get that ferris wheel scene with all the dateable characters, and the Aquarium just feels like a sick date spot.
I want them to get to look at cool fish and get to go on some fun rides, there's so much humor potential if nothing else!