Mysterious Girlfriend X (謎の彼女X, Nazo no Kanojo Ekkusu) is a Japanese manga written and illustrated by Riichi Ueshiba. It was originally published as a one-shot story in 2004 before becoming a serialized comic in Kodansha's Afternoon magazine in 2006. The manga is licensed in North America by Vertical. An anime adaptation by Hoods Entertainment aired in Japan from April 7, 2012 to June 30, 2012, with an original video animation episode released on August 23, 2012.