『a little far away.. Kusatsu Onsen (Kusatsu Hot Spring) (草津温泉-←tripadvisor site)』
I love Kusatsu Onsen very much. I visited many times. but a little far away from tokyo.
It takes about 3hours by train+bus from tokyo to Kusatsu Onsen.
The Hot Spring is very feeling good. very hot and a little stimulate to body because of strong acidity（ＰＨ2).
skin becomes smooth. It will be no Skin problems.and PH2 + very hot simulate inpact to not only body but also soul (release my stress).

I love soba(buckwheat noodles) shop name is kouhakutei（柏香亭）in kusatsu. (（柏香亭）)
very flesh soba and volume is good. I like tendon(天丼) of kouhakutei too.

and Manju of matsumura too.(松むら饅頭)

...but a little far away. so another good place here
『ASAKUSA sensouji(浅草寺) + skytree.(sensouji(浅草寺) ,　　 SKYTREE)』
famous place. you can feel japan in sensouji. and skytree nice view.

another place here. I like
『yokohama(横浜) kanagawa prefecture.』

Ｉ like walking about in this order.
chinese town → YAMASHITA park → Red Brick Warehouse →　minato mirai

chinese town .perhaps you can enjoy for example finding difference between Home country. or if you miss home country taste. I love sangokushi very much. there is statue of Kanwoo general(關 羽将軍). always I bought Steamed Meat Bun and keep walking and eating to YAMASHITA park.
YAMASHITA park is comfortable place. if it's sunny, nice breeze from sea. (YAMASHITA park)

next walking to AKARENGA SOUKO(Red Brick Warehouse (赤煉瓦倉庫))

next waking to MINATO MIRAI(MINATO MIRAI)

this two place, Night view is good.
If you can with reference . Im happy.
I wish you could find good place your girlfriend want to go somewhere :)