After a powerful foe met his end, Kaito and Lucia were finally reunited; but they don't live happily ever after. Though he promises to return to Lucia someday, Kaito decides to go to Hawaii, become a better surfer, and try to find himself again; but along the way, an accident causes him to lose his memory and he ultimately falls in love with another woman. In the mermaid world, things fare just as poorly: with Sara gone, a new mermaid named Seira has taken her place and constantly shows up in Lucia's dreams, warning her about troubles that lie ahead. As if things couldn’t possibly get worse, a new powerful villain named Mikeru has appeared; not even the strongest mermaid song can harm him! Can Lucia get back the one she loves and defeat her enemies?
Both shows are super girly, have a musical theme to them and are very family friendly. They also happen to both be season 2's. You'd probably like more of one if you enjoyed the more of the other.