In the distant future, human development has polluted the Earth's environment to its limit. The atmosphere is murky, many species have vanished, and the world has fallen into ruin.

In this dying world, a new existence that evolved differently from humanity was born. They are called "Delphiniums."

Delphiniums possess special organs inside their bodies and produce microscopic spores through respiration. These spores promote plant growth and have the power to revive withered lands. The plants and crops they grew brought forth rich harvests, restoring life to the desolate world.

Once, people revered them as "bringers of happiness" and treated them like messengers of God. However, it was discovered that the spores and plant-derived components of the Delphiniums were incompatible with human bodies, causing harm through long-term exposure.

A salvation for nature, yet a threat to humanity.

This fact birthed fear and prejudice, and the Delphiniums gradually became targets of persecution. The name "Delphinium," once given as a blessing, eventually became a symbol of terror in human society.

Having lost many of their kin, the Delphiniums who barely escaped with their lives built their own nation in a land far from human territory. A giant tree stands there, serving as the symbol of their life and culture. However, conflict was constant even in that nation. In order to survive within limited land and resources, confrontations between Delphiniums occurred. Even so, they joined hands to live for tomorrow.

Meanwhile, in the human nations, voices calling for the exclusion of Delphiniums as dangerous beings grew stronger.

Amidst this, there were those on the human side who sought coexistence through dialogue rather than a military solution. Guest is one of them, heading out on an investigation to uncover the truth behind the "pollutants" originating from the Delphinium lands. There, Guest encounters a single girl.