Akitsu

Akitsu, is a 'disused' Sekirei; Homura refers to her as 'Scrap Number'. She can't be winged by an Ashikabi or use the Norito (she is useless from MBI point of view). Akitsu's power is very strong, allowing her to fight on par with Sekirei like Homura (they have encountered each other 3 times so far). Despite the fact that she can't be winged, she considers Hayato Mikogami her Ashikabi because he took her in and she fears being thrown away again.

Like her power, Akitsu has a very cold and melancholic personality. She speaks very little in a neutral tone and appears to be forgetful because at one point it was noticed she wore no panties; it was first assumed she was ordered to do so by Hayato Mikogami, but then she revealed it was simply because she forgot to put them on. She also stated she was envious of Homura because for him it would still be possible to get winged and thus have an Ashikabi, something she can never achieve. She also appears to be polite and follow orders without hesitation.
Akitsu also seems to posses some knowledge on subjects like the first generation Disciplinary Squad.

(Sekirei Wiki)