Karen invites Jun'ichi and his school friends (including their teacher) up to a mountain hotel resort to make up for the events of the cruise ship party. While there, everyone continues to hang around and tease Jun'ichi, who is not impressed by their company. Karen takes this to mean that Jun'ichi is not satisfied with the luxuries of the hotel and so she takes the group on a long hike up to the Ayanokouji family's secret hot spring. There they learn that the secret hot spring is a co-ed bath, which causes some problems since there are guys and girls...