In the fourth episode of Dead Mount Death Play, the focus is on the Shinjuku Police Station and the Materials Compiling Group #3 (Comps-3), a team dedicated to solving bizarre cases that the public would find hard to believe. They discuss the remaining troublemakers on their list—the Grim Reaper, the fire-breathing beetle, and the lemmings, all of whom are still at large. The Comps-3 team attempts to connect recent events, such as a mysterious fire and human knots, to these troublemakers.

Meanwhile, Polka manages to transfer the original soul of Polka-kun into a stuffed animal, allowing Misaki to retrieve her drone. Polka expresses his need to replenish his magical power, which he can only do with the help of high-density mana stones, such as gemstones. However, he soon realizes that obtaining these gemstones in this world is a costly endeavor.

As the Comps-3 team continues its investigation, Misaki and Polka find themselves at Clarissa's bar, where they encounter Kouzaburou Arase, a detective from the Shinjuku Community Safety Division. Arase is known for his intimidating demeanor and interrogation tactics. Polka and Misaki manage to escape from Arase, who continues to eye the two with suspicion.

Later in the episode, Arase grows increasingly determined to uncover the truth about the troublemakers and their possible connections to Clarissa's bar. Polka, Misaki, and their friends must tread carefully and ensure their true identities remain hidden from the authorities.

The entire episode is packed with action, tension, and unexpected twists, showcasing the characters' ingenuity and their efforts to keep their secrets under wraps.