Yowai 5000-nen no Soshoku Doragon Iware Naki Yokoshima Ryou Nintei - Yada Kono Ikenie Hito no Hanashi o Kiite Kurenai
In which the title explains it all. The mc is a dragon who is infamously known but in reality, is simply a vegan and is kinda useless. Nevertheless, a nearby village sends a sacrifice, only, she seems TOO eager. The dragon, not wanting to kill her, sends her back to the village, but the girl sticks around and they go on an adventure together. Also, the girl is extremely powerful and good at magic. If you are looking for a good laugh, and enjoy fantasy and slapstick comedy, this is the manga for you.
Hualongji
In which our mc was originally a carp but was turned into a dragon for doing whatever the fuck he did (he climbed up a waterfall or something). After that, he got a human form and protected his people of the sea. For killing these people who were terrorizing his people, and so he got captured by this dude.
Where the Dragon's Rain Falls
In which our mc is a slave and one day, as he is doing something, he encounters a young boy, as well as a very nice looking man (if you catch my drift).
Kamisama no Uroko