Blood Contract by Cold Soul (Bing Ling) or 血色契約 by 冰灵
Novel Updates Page: https://www.novelupdates.com/series/blood-contract/
*Yes many of the raws are locked because of censorship but I linked it because it is the only place I found that directly supports the author; locked chapters can be obtained through pirate sites but I still strongly urge you to SUPPORT THE AUTHOR!!!
Because modern-day Zero accidentally transported himself to a foreign world, the first thing he saw when he opened his eyes was a giant slave ship and he became the ship’s new slave. This was a place where the strong ate the weak. As a new slave, he would have to face his slave master and additionally get bullied by others. The most unthinkable thing was that creatures known as vampires existed.
1-10* Translated by Polarbearadise; their site is down but apparently https://endlessyearningtrans.wordpress.com/ is re-posting. The chapters can also be viewed on an aggregator site, but please don’t make it a habit to read from there, support translators and use NU, use as a last resort in case sites go down ;-;
*denotes chapters with NSFW content