Maki is the owner of the bar that Lucia and her friends (including Kaito) work at. His wife passed away 10 years ago. He later supposedly fell in love with Nikora the manager of the Pearl Piari Hotel (or Pearl Waters in the manga). Maki asked Nikora's hand in marriage but she rejected it saying that she'll wait until he lets go of his deceased wife.

(Source: Mermaid Melody Wiki)