Miniature Garden of Eden

From Aerandria Scans:

Roku is a young boy who lives a colorless and dull life in a world, destroyed by natural cataclysms and pandemics. But one day he meets a mysterious boy called Matsuri who makes him work with him in the florist’s. While trying to discover the secrets that seem to surround Matsuri, Roku’s soul starts to recover its vivid colors.