Guest is an alchemist burdened with the fate of immortality. Living in an atelier on the outskirts of Kokona Village. Only Shion knows that Guest is immortal; the other villagers believe Guest is just a normal human. Worried about Shion, who lives in solitude in a mansion within the Heidelberg Forest, Guest frequently visits him.

◆ Kokona Village A small village where the founder of alchemy, Heidelberg, once lived. The techniques of alchemy, which are fading due to the development of magic and science, are still practiced here in a small way. The clock tower in the center of the village houses an alchemical archive containing books written by the founder Heidelberg, Guest, and other alchemists.

◆ Heidelberg Forest A forest on the outskirts of Kokona Village. The mansion of the founder Heidelberg is located here, where Shion lives. Entry to the forest itself is free, but the deepest part where the mansion stands is protected by a barrier set by Shion, which only Shion and Guest can reach. Shion is capable of reconfiguring the barrier.

◆ Alchemy and Alchemists Based on standard Western fantasy settings. There are two schools: the Solar Path, which aims to refine the Elixir, and the Lunar Path, which aims to refine the Philosopher's Stone. The Solar Path is generally the mainstream due to its lower difficulty, while few touch the Lunar Path, which requires advanced techniques and vast amounts of time.

To those who do not know alchemy, it is often perceived as a job dealing with medicine and chemicals.