Avsnitt 4

A girl is found dead in the swimming pool in her house. The cause of death is determined to be heart attack, and police rules the death natural. However, Utsumi spots a purple mark on the victim's chest, and asks the coroner to analyze it. It is revealed to be necrosis, which prompts Utsumi to consider the girl's death suspicious . It is later revealed that two more victims have died under the same circumstance, which strengthens Utsumi's belief that this is a homicide case.