sashihara is the naruto of akb
her hetare chara is the kyuubi inside her
chakra is funniness
when she is put to test, the hetare comes out, showing how funny she can actually be. just watch old variety shows, her senpais were so strong that the person sasshi couldn't take it by herself, so her inner demon had to take control of her body. it was a full display of power.
nowadays the hetare is sealed deep down inside her, and there is no one left strong enough to break the seal. all we have are glimpses of the 9 tails, like pic related and that banter between her and murashige at this year's janken.