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獣ヶ島 (Beast Island) — 2019 Pilot Gathering

A 2026 interview with the organizer traces Kemogashima’s beginning to 2019, when seven people attended. The organizer’s website separately identifies the 2021 gathering as the first numbered edition, so this is recorded as an unnumbered pilot/precursor. The exact date and venue within Megijima were not found. Sources: https://micetimes.jp/interview-kemogashima/ ; https://www.kemogashima.com/.