Backtagging?: Always! I do it too much.
Threadhopping?: Usually I'm cool with it, as long as you specify which character(s) you want to thread with there.
Fourthwalling?: Totally cool. Ryoji may do it himself with god characters because HEY I KNOW YOU.
Offensive subjects?: I'm usually open to anything, though Ryoji may clam up, depending.
Kinks?: I am up to playing mostly anything. Just ask and I will be happy to confirm!

Hugging?: Yes, always.
Kissing?: Of course! Especially if your character's cute~
Flirting?: Like Ryoji doesn't flirt with everyone already.
Fighting?: He'll be hesitant to do so unless you really tick him off, but go for it if you want your ass whooped by a skeletal nightmare monster. Or a giant winged goddess morph. Neither are really pretty.
Injuring?: If you can manage it, go for it. Ryoji is a bit hard to hit, at least in Thanatos and Nyx Avatar forms. If in his human form, though, he'll be nice and fleshy.
Killing?: FFFT HE'S ALREADY DEAD WHAT MORE DO YOU WANT. But sure, as long as you ask.
Using telepathy?: Do it if you want, but he's a traumatized kid. Whatever your character sees won't be pretty.

Warnings: Spoilers. Like all the time; it's hard to avoid with a character like Ryoji. If you'd prefer not to play with him to avoid those spoilers, comment here. He'll bring up death a lot as well, so if that makes you uncomfortable, let me know.

Also way too much flirting. Waaaaay too much.

For Castle Perrault: Ryoji is from January 31 on the male route.

Also, if your character has any connection to death (i.e., saw someone die, had a near-death experience, murdered someone, just dealt with the dead on a regular basis due to occupation or other circumstances), let me know, as there's a chance Ryoji might be able to sense that.