Sabikui Bisco, Vol. 4 (light novel) by Shinji Cobkubo

A divine flower that eats...mushrooms?! In the heart of Kyushu lies the Six Realms Prison. There, an android with the ability to tame the ravenous Shroom-eating blossom dreams of freedom. For the sake of the Mushroom Keepers'AEo way of life, Bisco will have to break into the prison and bust out the one person capable of pruning this problem before it blooms out of control!
Binding: Paperback / softback