Hashiri Nio is an energetic and upbeat girl with a knack for peeping into other people's businesses. Despite being a part of the Black Class group, she is also affiliated with the academy in some way.
Nio is the one who vaguely warns everyone of Haru's hidden nature. Nio also tells the group that the first person to kill Haru off gets any reward imaginable in order to set up some hype. She has also devised a system where everyone has one note that they are able to send to Haru as a warning that they are going to kill her. However, after sending the note, the sender only has 48 hours to finish her off, or be expelled.
Nio is always seen wearing full body outfits in order to conceal the large, bird-like tattoos she bears. It is revealed that Nio comes from the infamous Kuzunoha family, a feared family of skilled assassins that use illusions, and has no relatives. Upon meeting Meichi, Nio fell in adoration with her and vowed to give up her whole life to serve her. Meichi took her in, with Nio changing her last name from "Kuzunoha" to "Hashiri". Later, Nio attempts to assassinate Haru, while disguised as Tokaku, but ends up stabbed in the chest by the real Tokaku. Nio survives from being stabbed, despite no explanation being given on how it comes to pass, and in monologue congratulates everyone for graduating from Class Black.