Running annually since 1992, the Otofuke Tokachigawa Swan Festival celebrates the migration of around 1,000 white swans that fly into the Tokachigawa Onsen area each year. The event incorporates a laser show and a large-scale illumination of over 600 light bulbs and LEDs, and typically draws in around 60,000 annual visitors.
The event takes place from the mid January to late February timeframe, and the official dates are posted on the festival's website closer to when it commences. Do note that in the case of bad weather the event can be canceled, so keep your eye on the forecast!
Admission to the festival is free of charge.