Museum

The serial killer is laughing in the rain. Punishment: Dog Food—. Punishment: Know your mother’s pain—. Punishment: one split evenly—. Punishment: Forever beautiful—. The Frog Man from Hell executes his "punishments" ...

(Source: Kodansha USA)
Included one-shot:
Volume 2: Onna to Koroshiya (Girl and Killer)
Volume 3: Bokura wa Shinyuu to Iu Karada de (3 chapters)