I want to second Yokohoma as well. It’s very relaxed compared to Tokyo, has a area called Noge that’s full of rock/jazz bars, nice selection of affordable hotels, and you can embark on a day trip to Kanagawa and Enoshima during this time too. There are some beaches up and down the coast as well.

You will be able to do everything at a relaxed pace while being an hour train ride away from Haneda.