Quick answer — Eir Aoi performed 4 anime themes, including "IGNITE" from Sword Art Online II, "Iris" from Sword Art Online: Alicization, "MONSTER" from Classroom of the Elite 4th Season: Second Year, First Semester.
Eir Aoi performed the anime theme songs "IGNITE" (Sword Art Online II), "Iris" (Sword Art Online: Alicization), "MONSTER" (Classroom of the Elite 4th Season: Second Year, First Semester), "Sirius" (Kill la Kill).
Eir Aoi's first listed anime theme is "IGNITE", the opening of Sword Art Online II.
