– Itori is the maid of honor and Yomo the best man, obviously.
– Nico and Roma have wormed their way into being bridesmaids.
– Donato offered to perform the marriage, but upon his s/o’s disapproval, Uta allows Kaneki to do it instead.
– It’s a brief, unconventional wedding. I don’t think Uta or his s/o would want a crowded, fancy wedding. Though both are dressed up, I doubt they are in traditional attire.
– Touka and the rest of :Re are involved, of course, in setting up a small celebration.
– Uta is probably fed eyes instead of cake. Whether his s/o is fed eyes or cake depends on their species.
– There’s a lot of humor. Uta and his s/o adore weird jokes, and they coerce Kaneki into including them in the ceremony.