We went to Onsen (hot spring). With 2 under 2 years old, the places we can go are limited. It's impossible to go to Onsen hotels with big communal baths. It's impossible to go somewhere far but very nice, either. We ended up going to Izu Ajiro, where we can go by 2 Shinkansen plus a short local line ride. The accommodation have a small Roten Buro (outside onsen bath) in each room. They also have a time sharing Roten Buro. This small pot is the one we had in our room's balcony. The view of Atami from the bath was fantastic. Another one where Arata and Jason are in is the time sharing Roten. The water temperature was about 42C and it was too hot for Arata. He didn't like it because it was "Itai (sore)."