The story of "Thanatos's Bookmark Serial Killer and Literary Girl" begins with a scene called "Killer Barista", in which a serial killer who routinely drinks coffee after killing his victims is the talk of the town. Aside from high school friends who are excited to say, "It's a handsome murderer with a fashionable and sweet mask !!", Choko Mizuno, a literary girl who is aiming to become a novelist, said, "But I have no pride." If you kill a person and the purpose is robbery, it's thin as a murderer. " However, one day, a contact was made between Choko and the killer barista ...