「Mikazuki (三日月) – Ayaka」Wiki
"Mikazuki" was originally supposed to be Ayaka's first single but was pushed back. A music video was produced before Ayaka's first single, "I Believe", was even released. The song was used as a commercial song for a chain of Japanese record stores and later used for a drama known as @Human. When the single was released, it became Ayaka's first number-one single.
(Wikipedia contributors. "Mikazuki (song)." Wikipedia, The Free Encyclopedia. Wikipedia, The Free Encyclopedia, 11 Jun. 2014. Web. 26 Jun. 2014.)