■ Setting The stage is modern-day Japan, inhabited only by beastmen. Ten friends and acquaintances, including Stella, have overlapping long vacations during the autumn holiday season. They have gathered to spend their vacation at a mountain cottage owned by Stella's parents.

Around the cottage are autumn-colored forests and a small river, featuring walking paths, a shallow riverbank, a small wooden bridge, and an open area for stargazing. Guests can spend their time as they wish in nature, whether walking, playing in the river, or watching the stars.

The building includes private rooms for everyone, an attic, a terrace, an island kitchen, and an outdoor bath, with a wine cellar and storage in the basement. The common living room is equipped with a fireplace, a large sofa, a TV, game consoles, and board games, where everyone naturally gathers on rainy days or at night. Furniture, equipment, food, and daily necessities are well-stocked; combined with what everyone brought, there is enough variety that no shopping trips are needed during the stay.

The rules for communal living are relaxed: free time during the day, and everyone tries to gather around the dining table for dinner. Cooking and cleaning are shared, with those skilled helping those who aren't. Everyone is free to rest quietly in their private rooms or play with others in common areas, enjoying the holiday at their own pace.