Onsen day trip from Tokyo?

Hi,

I'll in Tokyo from May01 to 07 with a JR Pass. Looking for a day trip to an onsen. What would you advise?

Are you more interested in.

(1) Water quality?
(2) Ambiance of the town?
(3) Ability to easily get to the location from Tokyo in a day???

quite secret to most tourists and with many nice onsen on one spot is Nasu Onsen. (my recommendation as an onsen geek)

but of course there are many other options like Ito (Akazawa Higaere Onsenkan), Izu (Arai RYokan), Hakone (Yuryo), Karuizawa, Atami,.... and of course even in Toyko there are some good places to spend a day

Bessho Onsen is a pretty town and gets late Sakura. It was in full bloom in mid May when we were there. Water is sulphury but not as stinky as Hakone.

ah, Bessho is also absolutely great, yes. and has great temples also.
(but it takes about 1h more than getting near Nasu)

Hakone is very popular for people in Tokyo. Because there are lots to do besides onsen (museums, hiking, cruising on the lake, etc.); you can do stuffs during the day and bathe in the evening/night when those other attractions are closed.
https://www.japan-guide.com/e/e5200.html

Thanks. I'll look into all these tips.

For now I could only do a day trip onsen w/ easy access from Tokyo since my hotels are already booked. If I change it, I'll probably be paying higher hotel price. Would like to do one over night onsen but looks like it'll be during next trip.