The Herbivorous Old Dragon is Named the Evil Dragon - Coming Out of the Mountains and Entering the World

A 5000-year old vegan dragon was living peacefully when one day a young girl showed up in his cave. She offered herself as a sacrifice in order to gain favor for her village. He played along as the great "Evil Dragon, the Demon Lord's Army Leader" in order to get rid of her. However, his little white lie awoken her hidden powers and his peaceful life suddenly ended.

For 5,000 years, a harmless herbivorous dragon lived a quiet, secluded life. But everything changed when a girl called Reiko appeared before him. She offers herself as a sacrifice to who she believes is the evil dragon, Revandia, in exchange for helping her defend her village from the demon king. Together, the so-called “evil” dragon, devoid of flight or magical prowess, and the enigmatic girl embark on an epic, demon-vanquishing adventure! *Source: Manga UP! Global*