Staying in activities in Japan

I am traveling to Japan with an infant, so we won’t be able to get out and about for night life. Any recommendations on activities or things to do, especially if they are unique to Japan? On some days I’ll be with my husband too so one of us could go out and pick something up. I’d love to find fun things to do at night that aren’t just watching TV or bringing food back to eat (although I am VERY excited about the food)

We are staying south of Tokyo a bit