Aira is cosplaying as Sailor Venus from Sailor Moon. Sailor Venus, officially spelled as Sailorvenus in Japan, is one of the central characters in the Sailor Moon metaseries. Her real name is Minako Aino, a cheerful schoolgirl who can transform into one of the series' specialized heroines, the Sailor Senshi.
Sailor Venus is the fourth member of the Sailor Team to be discovered by Sailor Moon, though she was the first to awaken to her powers. She serves as the leader of the Guardian Senshi who protect Sailor Moon. She uses light and energy based powers, and often utilizes a special chain for melee combat. In the manga and anime series she dreams of becoming a famous idol, whereas in the live-action series her character is refactored to already be a celebrity.
She was first introduced as the protagonist of Naoko Takeuchi's much-shorter manga series, Codename: Sailor V, of which Sailor Moon is a sequel. In it (and the early part of Sailor Moon), she goes by the pseudonym Sailor V, short for "Venus", and is given personal backstory. The plot lines of Sailor V are generally compatible with the newer series, but are usually considered as separate. Later, she co-stars with Rei Hino in a special short story titled Rei and Minako's Girls School Battle.