Aneki means elder sister... was the main character a girl??? +__+ Normally you'd only use aneki/aniki to address your elder siblings, but you can also use it in the "frat" context. You know, where everyone is brother and sister and basically one big family. (i.e. among yakuza and other gangsters) From what I understand (from anime/J-dramas), aniki/aneki is used by dominant younger siblings. The "you're older than me but we're equal" type. A tomboyish girl might call her elder brother aniki instead of onii-chan. Whether this really happens in Japanese households nowadays or not, I don't know.