Mai Kuraki x Meitantei Conan Collaboration Best 21: Shinjitsu wa Itsumo Uta ni Aru! (倉木麻衣×名探偵コナン COLLABORATION BEST 21 -真実はいつも歌にある!-) is the fourth greatest hits album by Japanese singer-songwriter Mai Kuraki. It was released on 25 October 2017 by Northern Music, in celebration of Kuraki's long-time collaboration with the Japanese animation Case Closed. The album features all the songs Kuraki had written for the animation.