In 2015 released in Japan the PlayStation Vita version Irotoridori no Sekai World’s End the Irotoridori no Sekai World’s End -Re:Birth- in package and digital version (PSN). Hunex today announced that the digital version of the game will be available until March 30, 2017 in the Japan PSN and after that you can’t buy it.

If you already have the digital version you can play with it anytime and you can re-download it without any problems.
PSN: https://store.playstation.com/#!/ja-jp/cid=JP0746-PCSG00462_00-IROTORIDORINOSEK