ℬromance ୧✿✿୨ BL Subtext

Originally it was a oneshot titled Scrap Heaven, then it became a series named Gokurakuchou Dead End.
Raw: http://www.77mh.com/colist_238185.html

Novel: https://www.novelupdates.com/series/kyou-kara-ma-no-tsuku-jiyuugyou/ - https://www.baka-tsuki.org/project/index.php?title=Maru-MA
+ anime

Hisui, a merman with scarlet hair, belongs to a new species, a very rare type of sub-human-mermaid. Normally, such mermen have white hair, but in water the color changes. The aristocrats trade them for very large sums of money. Trying to escape from the lord who is keeping him, Hisui's path crosses that of the pirate Ikuta, who takes the marman on his ship and thus gives him freedom. From here, starts their journey together!
6 Volumes + Volume 6.5 (Hiatus) - Raw:
https://www.177mh.com/