The World Ends With You: Solo Remix is a port of the original DS game to iOS and Android, but ever since iOS 8 the game broke and was target of numerous rage reviews. SE claimed that it was working on a fix, but failed to deliver one even after 5 months since the release of iOS 8. This is what SE had to say:
“Upon examining the impact of recent iOS updates to the title, we determined that the affected areas were greater than originally assumed,” a representative told us via email. “We were working to address this matter, however, the title has been regrettably pulled from the Store. Square Enix is actively working with all related parties to make available the software update; however at this time, we are unable to communicate a clear and adequate timeline. We appreciate your patience and understanding as we work to determine a solution.”
The official website of the game has received a 404 treatment, indicating that this game has been abandoned. As far as the Android port goes, it's still available, but there are contradicting reports of users claiming the game crashes immediately upon start on Android 5 and needs a fix. My copy of the game does indeed crash on my Shield Tablet with Android 5.