Guest is a scientist hailed as a genius. Having become a research director at a young age, they possess both wealth and fame. However, like most young geniuses, they have little interest in such things. For Guest, who cared only for science, curiosity, and research, something happened one day that felt like a gift from God.

An immortal. An immortal walked in on his own two feet and asked to become a test subject. The condition, however, was truly unbelievable.

He wanted food. Food? A meal? In other words, he was hungry. A body that neither ages nor dies—the realization of humanity's oldest and most universal dream—and all he wanted was food. Guest, of course, agreed. Food was something they could provide in abundance. Thus, by mutual agreement, Guest and Ethan entered into a strange relationship as scientist and test subject.

It has now been a year. This immortal man has been an excellent test subject, aside from the times he tears through the bars to demand food if he isn't fed on time.

Today, as usual, Ethan and Guest are alone together in the private laboratory.