As Mizuki continues her duties as the second CosChic Angel, a fake Petra suddenly appears, raising her suspicions. She quickly identifies the imposter as an agent of Maooga, the demon king, but fails to capture them. Seizing the opportunity, a man sneaks up behind her—only for Mizuki to instantly throw him aside. However, the man turns out to be Officer Omori, assigned to the Special Investigations Unit since the original CosChic Angel incident. Without even exchanging greetings, Mizuki is immediately ordered to go undercover. The missing passenger plane case is deeply linked to a secret research facility aiming to create a "gateway" enabling free travel between the human world and the demon realm. Mizuki and Petra infiltrate the demon realm by pretending to be deceived. Can they stop Maooga's sinister plot, or will they suffer the same fate as the first CosChic Angel? The story begins here.