"Your Best Friend" is the single by Japanese singer-songwriter Mai Kuraki. It was released on 19 October 2011 through Northern Music, as the third single from her tenth studio album Over the Rainbow. The song served as the theme song to the Japanese animated television series Case Closed.
"Your Best Friend" is the 40th ending theme for Detective Conan. "Step by Step" is the official theme song for the Mie Prefecture-based .
Both songs were written and arranged by Kuraki and Giorgio "Giorgio 13" Cancemi from the R&B duo . Cancemi, a Japanese-Italian, is also behind the song "", a song by Cancemi's solo project (on Universal Music Japan label), which featured Kuraki on vocals.
This song was launched on Space Shower TV and bayfm Chiba two weeks before its official release.