I believe it was mentioned before (many, many times) that Yukari has powers that translate into world-hopping, convenient teleportation, and near-omnipotence in her own world of Gensokyo.
However, she is lazy, and will only really use any of this if she feels arsed to, or if she wants to troll the hell out of you. She can't technically mind-read, so this is a simple form to fill out:
Name: Who are you? WHO WHO, WHO WHO
Worldhop Permission: Can Yukari hop to your world without IC permission? If two people from the same canon give conflicting answers, Yukari will not be able to worldhop to the same rough area as any players that said 'no', but WILL be able to worldhop to that world.
Gap Trolling: Yukari does not always have to come all the way through one of her boundary gaps, nor does it need to be big enough for her to. There are examples in-canon of her taking items from a shop without ever getting close to it, as well as mentions of her stealing food or drink from others as casually as if she was right there. Fanon takes this to a
whole new level. So much so that there's
a pool on Danbooru consisting of fanart whose basis is pretty much "Yukari being a damn troll". (Warning: Being danbooru, many of those pictures are NSFW.) Is Yukari allowed to do use her powers to prank on your character? Don't worry - her pranks will (generally) be clean.
Gensokyo Limits: If Yukari pulls you to Gensokyo, or if you decide to go there herself, what is she not allowed to do to you?