Seijoku no Mori

In a certain era, the race of elves has been cursed. The flowers they care for wither and die, and whatever plant they water loses its seeds.
A certain researcher ventures to an ancient city and obtains the only copy of a book that documents the first forest of the elves.
In the book he finds records that differ from the lore that is handed down elsewhere. They are about the activities of the monsters who dwell in the forest, and about atonement.

[From DLsite English]