Sun is a librarian, along with a secret murderer. He is a massive clean freak that must have everything tidy and organized, and always wears a cute sweater each day at work. He has reading circles and book clubs for kids that like reading. 

As a murderer, he's crazy and sadistic. He always wears black gloves and a black apron so he doesn't get blood on him, and always helps track targets and cleans the crime scene. Him and Moon are both killers and work together. He often flexes his gloves.