Rena "Airi" Sako (迫亜衣梨, Sako Airi) is a shinigami of the Fourth Division and a recent edition to boot, holding the Seventh Seat. Although her birth name is Rena, she prefers to go by Airi as she feels as though it fits her more. Following the invasion of the Engelhaft Gewitter, she was one of the many Shinigami who were trained and distributed to various divisions in order to make-up for the lack of manpower.
Airi seems to be a frigid, strong, and serious woman. In reality, she is prone to doubting herself and has a good sense of manners. She is compassionate about helping and saving people to the point that, although being loyal to Soul Society, she questions the morality of their conduct when it comes to dealing with outsiders. Because she has been working for so long with trying to get through the academy, she rarely gets any chance to blend within girls her own age like she used to, and thus, has problem interacting with people normally. This usually leads to Airi making mistakes and acting flustered when anyone notices and points this out. The notable example is when she once barged into Sanosuke Hotsuin's re-assigned room without asking permission, and after he pointed this out, she apologized and has never done it again.
It is implied through events that she may have feelings for both Sanosuke and Haruki Satonaka, and acts very flustered when these feelings are implied by Yoshino Komaki, who bears similar romantic interests in both men. Although she becomes very nervous when her romantic feelings are brought up, Airi typically denies every claim brought forth. This leads to many people thinking that she is unable to care about others on any level other than a professional one, much to her dismay.