In a distant future where the sun no longer shines, Toshiro Kamiya gives up his body to a sinister floral metamorphosis for a payday.

The earth of the distant future is covered in thick clouds, and the sun no longer shines. Plants wither, and oxygen is thin. To fight extinction, humankind has developed a technology that turns humans into plants, providing a small amount of oxygen. Is this process sustainable? Is it ethical? Toshiro Kamiya must consider these questions as he's faced with a difficult choice-save his family or save himself.

Struggling in poverty and slowly transforming, Kamiya must figure out how to spend the two brief years of humanity he has left after undergoing the transfloration procedure. The vine growing from his stomach has made him question his relationship with his mother and his employment at Transflora Medical. Meanwhile, Kamiya's childhood friend Hourai assists in the investigation of a string of murders committed by a spiriflor.