Kazuki: Nothing physical will change. He'll be more relaxed and upbeat, rather than having a slightly awkward side (not that that really shows much at all), or uneasy with their situation. At times he displays an almost childlike curiosity towards things, so that may surface all the more with so many things to try and explore, even if they may be nothing special to anyone else.
. . .And of course, as Xae had mentioned, he and Soushi will definitely be all about and around. Kazuki probably glued to his hip.
Zero: More chill in general. Which may possibly equal to his more kinder and teasing side coming out. He also may try one of those actual!bloody marys, as any other time he's not interested in alcohol (or blood from anyone but Yuuki). And speaking of, he'll definitely be around his family a lot, too. — Generally speaking, though, nothing drastic will change.
Jae-Ha: On top of everything else, he will be very carefree about whether or not people see his dragon'sleg! Something he is always very adamant about not letting ANYONE see. So I've really been wanting to have others learning about for a long while, now. 8) In general, though, he's usually very relaxed.
Please note, however-! He may be much more flirtatious which also means more touchy-feely or disregarding any personal bubbles towards any given person (esp cute girls, but good looking guys aren't completely exempt!). He (still) does know how to be appropriate, though, and not likely to be straight up lewd. Still, though, depending on the character, it could still be seen toeing the lines of sexual harassment (never minding how I don't like phrasing it that way OTL;;;)
Sai: Although lowered inhibitions can mean him being much more violent (even murderous or manic), I kind of want to branch off into a part of him that doesn't show very often: That being his very playful side, even to the point of giving off a childlike innocence (granted a part of that may be on purpose). He'll naturally still be a brat, but the environment will bring out a lot of curiosity for him, and of course ALL OF THE FOOD. He never had a real childhood, so he's really just going to have fun. —And also much less of a creep. 8)