Upon receiving an invitation to a treasure hunt from the famous mysterious item artist Reinette, Ramune and Kuro visit Reinette's mansion. There they encounter Ayame and Nico, who have also come to participate in the treasure hunt. However, when Ramune sees the man with them, his expression freezes, and he attempts to flee the scene. That man is Ramune's master Momiji!
On the night of the full moon, 
the correct door will open.
.في ليلة البدر، سيفتح الباب الصّائب
In einer Vollmondnacht
wird sich die richtige Tür öffnen.
Cuando haya luna llena,
la puerta correcta se abrirá.
La bonne réponse apparaîtra
un soir de pleine lune.
La porta giusta si aprirà la notte di luna piena.
Numa noite de lua cheia,
a porta certa se abrirá.
В ночь полнолуния откроется
нужная дверь.