Regret by Sophie Stern

Once upon a time, she was a princess.
Asherah lives on a planet filled with underwater palaces and beautiful cities, but she’s trapped. Unable to breathe underwater like her counterparts, she’s destined to live a life of solitude and isolation. When an alien from Malum arrives to return her traitorous brother to the queen, she realizes that there might be more to life than following the rules and writing policies.

Lion is a guardian for the king of Malum. Together with his best friend, Alixei, he helps protect the king against any threat imaginable – including traitorous little princes. When Alixei returns to Malum unexpectedly, Lion is left on Oceaile with a prince, a princess, and a whole lot of questions as to what he should do next.
Where has the queen gone?
Why can’t anyone find her?
Does her disappearance have anything to do with the prince’s recent trip to Malum?
And why can’t Lion take his eyes off of Asherah?