She is Ōotori's 8 year old cousin that was introduced into chapter 68; she is an aspiring ninja and wishes to be the best within the family; seeing to do this as to take the life of her cousin.

But she is still at an amateur level (hiding with wrong patterned wall paper, her disguises still revealing her short height, and unable to keep herself from falling off the ceiling). But it is soon found out that she has Hachibe's ideal hands and he constantly tries to cover them with some kind of jam (which results in Ōotori protecting her cousin from him).

But then Ai pulls out a dangerous bomb in which Hachibe's berserker mode was able to kick it out of the distance just in time and for this it seems that Ai has developed a crush on him (and might have revealed that Ōotori has one on him as well).