Private onsen in Kanagawa
A bath you have to yourself: no other bathers, and usually no tattoo problem either.
Is there a mixed onsen in Kanagawa?
Yes: Shumeikan. If what you want is to bathe together as a couple or a family, a private onsen is usually how it is done in Japan: the 21 below have a bath your group uses alone. Where Japan’s mixed baths are, and what to wear

Nanasawaso
七沢荘
Visited · No.9OK in a private bath (day visit)OK if covered (overnight)Private bathDay visits without staying
Hakone Yuryo
箱根湯寮
Tattoos OK (day visit)Private bath
Hakone Kowakien Motoyu Mori no Yu
箱根小涌園 元湯 森の湯
OK if covered (day visit)Private bath
Yunosato Okada
湯の里おかだ
Tattoos not allowed (day visit)Private bath
Kappa Tengoku
箱根湯本温泉 かっぱ天国
Policy not published (day visit)Policy not published (overnight)Private bathDay visits without staying
Yoshiike Ryokan
箱根湯本温泉 吉池旅館
OK if covered (day visit)OK if covered (overnight)Private bathDay visits without staying
Hakone Kowakien Ten-yu
箱根小涌園 天悠
OK in a private bath (overnight)Private bath
Hakone Hotel Kowakien
箱根ホテル小涌園
Policy not published (day visit)OK in a private bath (overnight)Private bathDay visits without staying
Hakone Yumoto Tenseien
箱根湯本 天成園
Tattoos not allowed (day visit)Tattoos not allowed (overnight)Private bathDay visits without staying
Hakone Kowakien Mikawaya Ryokan
箱根小涌園 三河屋旅館
OK in a private bath (overnight)Private bath
Gora Hanaougi
強羅花扇
Tattoos OK (overnight)Private bath
Hakone Gora Onsen Kinoyu Setsugetsuka
箱根強羅温泉 季の湯 雪月花
OK in a private bath (overnight)Private bath
Centurion Hotel & Spa Hakone Bettei
センチュリオンホテル&スパ 箱根別邸
Policy not published (overnight)Private bath
Susukinohara Ichinoyu
仙石原 ススキの原 一の湯
OK if covered (day visit)OK if covered (overnight)Private bathDay visits without staying
Mount View Hakone (Kawawaki-no-yu)
川涌の湯 マウントビュー箱根
Policy not published (day visit)Policy not published (overnight)Private bathDay visits without staying
KAI Hakone
界 箱根
Tattoos OK (overnight)Private bath
Yumoto Fujiya Hotel
湯本富士屋ホテル
OK if covered (day visit)OK if covered (overnight)Private bathDay visits without staying
Hotel Okada
ホテルおかだ
Tattoos not allowed (day visit)Tattoos not allowed (overnight)Private bathDay visits without staying
Hakone Suishoen
箱根・翠松園
OK in a private bath (overnight)Private bath
Hakone Ashinoko Hanaori
箱根・芦ノ湖 はなをり
OK in a private bath (overnight)Private bath
Tonosawa Ichinoyu Honkan
塔ノ沢 一の湯本館
OK if covered (day visit)OK if covered (overnight)Private bathDay visits without staying