Chiikawa: Ningyo no Shima no Himitsu

Based on a series of Chiikawa comics posted on X by Nagano from March to November 2023, known as the "Siren Arc" . One day, while Chiikawa and Hachiware were relaxing in the square, Usagi suddenly appeared with a flyer stuck to its face. When Hachiware checked the flyer, it was an invitation reading