Katahara Onsen is a scenic hot spring village in the coastal area of Mikawa Bay, considered as one of the larger Gamagori Onsen area. The area around the Hodagaike Pond, part of the Katahara Onsen, is highly regarded as "Home Place of the Hydrangeas" (Ajisai-no-sato), due to the 50,000 bushes of the exuberant flowers that proudly ornate the boardwalk around the water body when in their full bloom. When it happens, the "Ajisai Matsuri" (“Hydrangea Festival”) is held in order to celebrate them. It starts on June 1st and goes for a whole month until June 30th. And the event is quite famous: the event attracts an excess of 100,000 tourists yearly, and temporary bus lines operate during the period in order to facilitate the access. The hydrangeas are also artificially illuminated after dusk, giving the place a whole different way to enjoy the place. And if you're lucky, you may even get to see the beautiful twinkling firefly swarms that chose this incredible place as habitat.