Chuzenjiko Onsen is connected with central Nikko by Tobu bus. The buses leave from JR and Tobu Nikko Station and are bound for Chuzenjiko Onsen or Yumoto Onsen. There are about three buses per hour. The one way trip from Tobu Nikko Station to Chuzenjiko Onsen takes about 50 minutes, costs 1150 yen and is covered by several Tobu free passes.
A 2-day pass for unlimited bus rides between Nikko and Chuzenjiko Onsen is available for 2000 yen at Tobu Nikko Station.
Note that during the autumn leaf season in October, traffic between central Nikko and Lake Chuzenji can be very heavy, and buses can incur heavy delays, especially on weekends. The Irohazaka Winding Road becomes particularly congested. If possible, try to visit during the week and not on weekends.
Sightseeing boats can sometimes double as a way to get between destinations around Lake Chuzenji, although they would only make sense if the original intention is to tour the lake by them. The sightseeing boats making a loop around the lake (one hour, 1250 yen, hourly departures) operate only from the second week of April through November. From Chuzenjiko Onsen, these boats make stops at Shobugahama (20 minutes, 600 yen) and close to Chuzenji Temple (50 minutes, 1150 yen). Infrequent boats go between Chuzenjiko Onsen and Senjugahama from June through September (40 minutes, 940 yen).
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