A Dance of Memories and Time

Two best friends suddenly realize that they can't live without each other (born the same day, live next to each other, take all the same classes). When they realize that one of them might outlive the other, and every option they come to ends with the result one girl living a longer life than the other, they decide to make a deal with Keres - an ancient spirit that constantly makes deals with mortals - for immortality for both girls, but on one condition. Although immortal, they can be harmed by only each other as well as have a chance to become mortal once again if they find true love, meaning the girls are only half-immortal until the other dies and the rest of their soul goes to Keres.

Every year they end up in different timelines and they have to find each other in that timeline, having to convince the other on whether to continue this routine for another year or not before appearing in a different timeline to do it all over again.

One year however, Calypso meets a group of royal siblings who agree to help her find her friend once more. They go on a wild adventure as she begins to fall for the eldest sibling - Sorin - but as she tells them the consequences of her actions, she realizes that love can't - and won't - always help her in this situation.