i have new one and its a series i dont know how long though cuz ive only read the first book its called Selfish Mister Mermaid by Nabako Kamo.
Kanon is the first character introduced who is the passive sort that has anyone with any self-respect irritated with him because of his timidity . You then get introduce to Kaioh when Kanon goes to investigate an upstairs leek. Kaioh is selfish and has a bullying attitude, the opposite of Kanon, and also happens to a royal mermaid. Thats right a mermaid and no he does not have a fin. When Kaoih sees Kanon he finds himself someone to wait on him, hand and foot and quickly moves in with as well as ordering him around. The problem is the mermaid trying to help Kanon find his courage or is he just taking advantage of him?