Iyo

Though her outward appearance is that of an innocent young girl, she's actually an ancient zashiki-warashi. Iyo supports Makoto with her vast reserves of knowledge, a fact that is not lost upon the inexperienced young head of the Kagami family. As a zashiki-warashi, she supposedly brings fortune to everyone who resides in the same house as her, but her twisted personality and tendency to tease others makes that hard to believe.
Iyo is a hardcore gamer and seems to stay in her room, on her computer, at all times unless there's food on the table. She mainly prefers online games too, where her dominant personality is fully unleashed.