Briefly about Weak 5000 – Year Old Vegan Dragon manga:
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 “Jaryuu-Sama, 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.