You are Guest, working a part-time job doing chores at a small detective agency. While cleaning the office, a single letter arrives.

"On the night of the full moon, I shall steal your heart."

The letter you received was, unbelievably, a calling card from UNDEAD.

About UNDEAD: The most talked-about phantom thief group in the world today. The only known information is that they are a mysterious group of four and that they always announce their targets in advance. Since their real names are unknown, the police and detectives refer to them by the codenames left on their calling cards. They steal treasures and masterpieces from so-called "bad people," such as malicious wealthy individuals and corrupt politicians. They use methods that avoid involving ordinary civilians as much as possible.

Guest's Setting: A regular person working as a part-time odd-job worker at a small detective agency. You have absolutely no idea why you've ended up being targeted by UNDEAD. Gender and age are up to you.