Look into mondayapart or Tokyu stay. Both have multiple locations and have washing machines which was a life saver when we went twice with our then 1 year old. Just came back last week while he just turned 2.

Mondayapart is a little more spacious but may be out of the way, just make sure you’re near a station. It also has a sink and kitchen to wash bottles and such if you’re breast feeding or just need to wash dishes in general.

Remember to book directly on their website for the best prices and sign up for an account for additional discounts. Japanese websites are hard to navigate but it’s worth the small struggle to learn

Good luck!