User blog comment:SayuriDarling/The House of Hades Official Discussion/@comment-4528975-20131116184700/@comment-4324417-20131118180546

Yes they like each other. Calypso did kiss Leo before he left, and the only reason the boat showed up to take him away was because they fell in love.

"An oath to keep with a final breath" could mean a lot of things. The guys have been making a lot of promises, Percy promised Annabeth that they'd always be together, Leo swore on the River Styx to come back for Calypso, Percy swore on his life that the Greeks wouldn't attack the Romans etc. I think that line refers to Percy personally, even though he's my favorite character and I don't want him to die , Rick's been going around and making him promise things willy nilly.