Nightwing
Although Nightwing is commonly associated with Batman, the title and concept have origins in classic Superman stories. The original Nightwing in DC Comics was an identity assumed by alien superhero Superman when stranded on the Kryptonian city of Kandor with his pal Jimmy Olsen. Drawing inspiration from Batman and Robin, the two protect Kandor as the superheroes Nightwing and Flamebird. Following the Crisis on Infinite Earths continuity reboot in 1985, Nightwing was re-imagined as a legendary vigilante from Krypton whose story inspires Dick Grayson's choice of name when he leaves behind his Robin identity.
Night Wing
"Night Wing" is Kudo's first single to be released as a double A-side, with "Yukigasa". Her 1998 single, "Kirara", and its coupling song, "In the Sky", received a similar treatment, but was never officially released as such. "Night Wing" was written and composed by Miyuki Nakajima, and arranged by Ichizō Seo. The song marks Kudo's first collaboration with Nakajima in two years, since "Clāvis (Kagi)". It is described as a powerful midtempo song written by an invigorated Nakajima. Lyrically, the song describes a protagonist metaphorically "spreading her heart-shaped wings and soaring through a windy sky" and ambiguously pondering about her contradictory actions and mixed feelings. The song is composed in the key of A-sharp minor and Kudo's vocals span from G to A.