Kase River Firefly Festival — June Bioluminescence
The Kase River and its tributaries in the southern Saga mountains host one of Kyushu's most concentrated firefly populations — the combination of clean water, low agricultural chemical use, and dense riparian vegetation has maintained conditions for Genji-botaru (the large Japanese firefly) that have disappeared from most of Japan. The firefly season runs June 1–20, and the peak nights (June 8–12 in an average year) see thousands of simultaneous light signals over the river.
Essential Information
Opening Hours
June evenings only | From dusk (approximately 7:30 PM) | Peak viewing: 8:30–9:30 PM
Closed: Outside June 1–20 | Rain reduces firefly activity
Entrance Fee
Free
Best Season
June 1–20 | Peak: June 8–12 (average year) | Check local reports for exact peak
Visit Duration
1.5–2 hours (evening viewing)
Getting There
Access Information
Insider Guide
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