A Herbivorous Dragon of 5,000 Years Gets Unfairly Villainized(2018)

Yowai 5000-nen no Soushoku Dragon, Iwarenaki Jaryuu Nintei: Yada Kono Ikenie, Hito no Hanashi wo Kiite Kurenai

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!)