Firefly Watching at Osawa-no-Sato in Mitaka: Peak Season in Mid-June
Tonight, why not head to Osawa-no-Sato in Mitaka City to see wild Genji fireflies — a rare sight in Tokyo? This small municipal nature park, fed by spring water along the Kokubunji cliff line, preserves rice paddies, a wetland garden, and a thatched Edo-period farmhouse with a working waterwheel. Every mid-June, tiny lights flicker quietly among the waterways.
About Osawa-no-Sato
Osawa-no-Sato is a compact nature park maintained by Mitaka City. It preserves a wetland garden, rice paddies, a thatched farmhouse, and a waterwheel from the Edo period. Natural spring water feeds the park's channels, creating conditions where Genji firefly larvae can grow undisturbed — a rare example of wild firefly habitat surviving inside a major city.
Over 38 Years of Community Conservation
Firefly conservation at Osawa-no-Sato began in 1988 and has continued for over 38 years. Volunteers maintain the rice paddies, protect kawanishi snails (the fireflies' primary larval food source), and remove invasive species. The site is also used by local elementary schools for rice-planting programs, connecting children with ecosystem conservation.
Tips and Rules for Watching
Peak season is mid-June, with fireflies most active between 7 p.m. and 9 p.m. after sunset. Visitors must avoid flashlights, phone screens, and camera flashes, as artificial light disrupts the fireflies' mating signals. Loud noise and catching fireflies are strictly prohibited. Let your eyes adjust to the dark and simply observe.
Getting There
The park is about a 30-minute walk south of JR Mitaka Station. Alternatively, take a bus toward Shindo-Higashi or Osawa Community Center stops. Many visitors enjoy approaching via the Tamagawa Josui promenade at dusk for a scenic walk through the greenery.
Head to Mitaka Tonight for Fireflies
For over 38 years, volunteers have quietly protected these small lights. Put away your phone, stand in the dark, and take in the natural glow. A summer evening at Osawa-no-Sato, watching fireflies drift above the waterway, is one of Mitaka's most special seasonal experiences.