Renko Usami: Absolutely no out of the ordinary disadvantages. She'll have to go to classes and she'll spend time with her friend, but you'll see her most of the time. Hey, you might get to go exploring with the
SoS brigade Girl's Sealing Club!
Maribel Haan: Same as Renko.
Yumemi Okazaki: Chances are, she has work 24/7. When she's not teaching, she'll be working on her own magic theory, so don't expect to see her much unless you're a scientist on her level, specializing in a relevant field.
Chiyuri: Works alongside Yumemi. You'll probably see her more often, as some of the work she does is probably at a lower level (mopping the floors of the space-time probability vessel).
-Now entering a somewhat friendly gensyoko. Universal downsides: Crappy internet access, shortage of flush toilets and indoor plumbing-
Satori: First things first, throw those ideals of privacy out the door, and do your best to not think of memories you want to keep secret. Satori can know excact what you're thinking so long as she's close enough, even the fleeting thoughts that may cross your mind at the same time Satori crosses your field of vision (if you're a normal person in this respect, she might appreciate the complement of being pretty). As for the pets, stay away from them. Each and every one has the potential to seriously injure you, or even give you cancer. Being animals, they'll never be friendly 24/7, especially towards newcomers. Hope you're good with cats!
Koishi: Stay the hell away from Koishi. She is a powerful youkai with an unpredictable, naive and somewhat childlike personality. She can and will alter the subconcious of others. She may do anything with this ability of suggestion from forcing you to be her friend to getting rid of your own friends, and making sure you never notice the loss. However, she is so unpredictable that she may do nothing at all. Proceed with caution.
Yuugi: RUN. FOR. YOUR. LIFE. Unless you're good at danmaku, stay away. Logically, if she can't test her strength with danmaku, she'll resort to her other method. Fists. She does enjoy fighting, after all. Only safe for the ridiculously strong and skilled.
Parsee: May attack out of jealousy like she did to Reimu/Marisa.
Yamame: Her species doesn't eat humans, and she seems friendly enough, not attacking Reimu/Marisa until she thought they were up to no good. Might make you a bit sick, but only on purpose. Her living conditions are not the best for a human. I don't remember the tunnel in stage one ever being stated to be horizontal, and you do progress
downwards for the first stage or two....
Byakuren and friends: So long as you're accepting of youkai, it's a normal temple life, with all the "downsides" of a temple life.
Nue: Outside of the byakuren crew, she might be a bit dangerous, considering she's a nue. Her true form is thought to be a sort of chimera, and she just loves to terrify (not suprise) humans. Great companion for a troll of equal prowess. Otherwise, you'd be sick of her after no less than a day.
Kogasa: UMBRELLAS EVERYWHERE. EVEN IN THE TOILET. She won't enjoy your company if you're not very excitable, you boring person you.
Remilla: If you live with her, you are A: A maid, B: Patchouli, C:
China Hong Meiling, or D: Locked in the basement. No exceptions. And the positions for Patchouli and Hong are already filled.
Marisa. If you're an independent, fun loving, risk taking person, you probably see as many downsides as Marisa does. Zero. Otherwise, you're living in a forest filled with magical creatures with a teenage girl who likes to blow things up. It doesn't seem bad at first, until you realize you're living in a forest filled with magical creatures with your only companion being Marisa. Don't worry, you'll get by somehow.
Alice: Scenario A: You're turned down at the door. "Don't bother Marisa either, you lech". Scenario B: You're turned down at the door. Canon Alice doesn't want your company, she has magic to study and dolls to make. Scenario C: You're brought inside the house, and after a short period you are asked to help with the dolls and magic or get out. Scenario D(eredere up to 11): You're dragged inside the house, hugged, sat down on the couch, served tea, you have a long (awkward for you) chat, dinner, go to sleep, wake up to breakfast in bed, have a fun day working on dolls and trying a bit of magic among other things, and so on. How often does this girl get company, anyways?
Reimu: Not going to help around the shrine? Forget about staying there. You could be still be friends, though, granted it benefits Reimu and her donation box.
Yakumo family: The most unpredictable bunch in Gensyoko. You could probably befriend chen, and MAYBE befriend Yukari (it's been done before, however, the person who did it is now dead). Ran is too busy to put up with any shit. Disadvantages? If you're living with them, you're probably a shikigami, or a near-eternal ghost who wants to get away from the afterlife for a bit, IE: Yuyuko.
Yuyuko:
You are dead. That's all there is to say on the matter.
Kotohime: She's nuts. Unless you're nuts too, you wont be able to stand her.
Rikako: Those without mechanical experience need not apply. Otherwise, fun times advancing science and technology in gensyoko!
Nitori: She's alot like Rikako in ways, however, she's a kappa. And what do kappa eat? Anus marbles and cucumbers (bring lots of those). However, on the bright side, she might befriend you regardless of mechanical experience!
Aya: You're too zetta slow. Also, she's a reporter for the
national inquirer bunbunmaru, expect the usual.
Hatate: Like, forget about living with Tengu. They are extremely, like arrogant and totally look down on humans. Although Hatate totally doesn't publish a bunch of slander and embarassing articles, her basic personality is like, not the most pleasant thing ever.
RInnosuke: He's a nice guy. The most you'll have to do is help at the store a bit
and maybe get a little closer with Tokiko. If you knock anything over or dare shoplift, however,
better watch your back boy keep runnin.