Onaji Koin

Onaji Koin is a 2016 psychological thriller and occult detective anime. It follows the story of two intelligent minds; police detective Sachihiro Hikari and serial killer Daichi Daku, in a psychogical battle with Hikari fighting to catch Daku and stop the murders while Daku is fighting to eliminate anyone pursuing him including Hikari and continue the murders.

Plot
Onaji Koin is told through the actions of Saichiro Hikari and Daichi Daku. The 28 year old Hikari is shocked upon a series of murders in Tokyo, Japan when the killer is unknown and is an intelligent serial killer who leaves without a trace. Hikari is determined to arrest the murdered for the crimes and end the deaths; firstly, Hikari decides to search for clues at the murder scenes until a message is found carved in the corpses' scalp "LOOK CLOSER DETECTIVE". The corpse is then sent for an autopsy to be performed by professional surgeon Andrae Buroka, who is a friend of Hikari, and discovers a tiny chip inside the victim's brain.

In another scene, Daichi Daku is shown and meets a homeless man called Taichi Magukappu, Daku claims to want to help Taichi by first buying him some food and then offers a place to stay for the night and even a meal. Taichi is interested in the offer and agrees but also wants to do work and asks if Daku can also help him with that, Daku claims he could help. It then goes back to Hikari, who analyzed the chip and discovered a code that is encrypted to lead Hikari to an abandoned house.

Meanwhile, Daku is shown leading the homeless man to the same house and promises him some food but sitting him down on the couch. However as soon as the homeless man is settling in, Daku kills him by sneaking up from behind and using rope to strangle him to death, Daku is then revealed to be the serial killer and grins at his kill. Returning to Hikari, he enters the warehouse to find the corpse of the homeless man who had been hidden. Hikari then discovered fingerprints which leads to Yuri Taisho; an associate to untouched crime lord Nariko Kogo and is also known to manage her drug operations. Hiroki chooses not to jump to conclusions and assume Yuri is responsible, instead deciding to investigate.

Hikari then confronts Yuri and finds out he is not the killer but may be involved somehow, Yuri catches on Hiraki's suspicions and knocks him unconscious, capturing the police detective. Meanwhile, Daku is shown speaking to a corpse (who is facing him in first-person view) and talks about how to kill; stating the murder is easy while hiding the body is the hardest part, then smiles creepily before revealing he has chosen what to do with this corpse; dismember it and hide it in a refrigerator. Then it goes back to Hikari; who wakes up and talks to both Nariko and Yuri. Hiraki then talks privately to Nariko; telling her Yuri may be doing something without her awareness and wants to investigate him, Nariko reluctantly agrees but on the condition he ignores any crime she commits along with her empire. Then Hiraki manages to question Yuri until he admits his involvement: turning a blind eye to the killer's crimes and selling drugs to him as well as even providing him with a warehouse.

Niroki is enraged at Yuri's secrets and putting her organization at risk by selling her product and one of her warehouses to a serial killer. Hiraki attempts to uncover the killer's identity, but Yuri claims he was wearing a mask and to make up for his mistakes; he willingly gave Hiraki a list of his buyers and the location of the warehouse. Before investigating, Hiraki secretly tipped off the police department he works at to arrest Yuri and Niroki.