Yunessan

From Shinjuku station, take the Odakyu line Romance Car to either Hakone Yumoto station or Odawara station. Then get on either the Hakone Tozan Bus or the Izu Hakone Bus and get off at Kowakien bus stop. It's right across the street from the bus stop. I would go on a weekday if possible because it can get really crowded on weekends.
https://www.yunessun.com/en/