Once upon a time, two little orphaned girls grew up together in a remote village. When Avis, a master alchemist, encountered them one day in his travels. He took them in and trained them in his school of alchemy.
As the two sisters grew up, they both showed the potential to become great alchemists, although they were otherwise quite different. The younger one, Coral, was ambitious and mischievous, while the older one, Iris, was shy and humble.
One day, Coral's curiosity led her to a secret book that described an incredible potion: one that could grant eternal life.
However, Coral's ambitious attempt to make this potion came at a tragic cost: the death of her sister.
Unable to tolerate such a fatal error, Master Avis expelled Coral from the school of alchemy despite the great potential she showed.
However, Coral is determined to atone for her error and undo its damage. She vows to return one day and revive Iris once she has the knowledge to do so. She'll do whatever it takes, even if she has to travel to the end of the world.

In the end, Coral's plan succeeds. She revives Iris, who forgives her for what happened. Master Avis invites both of them to return to their studies at the academy.
However, Iris's brush with death has left her eager to see the outside world, and Coral can't forget all the people she helped through her shop.
They decide to leave the academy and explore the world together, so that they can use their skills as alchemists to help as many people as they can.