Hiiragi

{OOC}

Backtagging: Yes. As far back as you want to go.
Threadhopping: Yup, as long as it is not locked.
Fourthwalling: She fourth-walls all the time, if your canon knows anything about Hanamaru Kindergarten then feel free.
Offensive subjects: If your character is comfortable saying offensive things to or around a five year old then go for it, though she might not understand.


{IC}

Hugging this character: Sure, go for it, especially if she knows you.
Kissing this character: Again, if she knows you feel free...on the cheek.
Flirting with this character: Are they getting married? She might not see flirting the way you do because of Anzu and her own skewed ideas where adult relationships are concerned.
Fighting with this character: Play fighting, yes. Just let her get her samurai costume out.
Injuring this character (include limits and severity): No normally, unless there's a really relevant reason for it.
Killing this character: No.
Using telepathy/mind reading abilities on this character: Go for it, but she's five so don't expect to learn anything profound.

{Fourth-Wall Opt Out}

Hiiragi's canon likes to obliterate the fourth-wall and Hiiragi is guilty of breaking it herself. There are a number of references and shout outs to various other canons and here's a small list of what I can remember:

Full Metal Alchemist
Shaman King
Gurren Lagann
Gundam
20th Century Boy
Detective Conan
Evangelion
Planet of the Apes
Star Trek
Ultraman
E.T.
Star Wars
Warhammer
Dragon Quest

If you don't want her breaking your fourth-wall let me know and it'll all be good.