The National Museum of Japanese History
The museum is located in Sakura City in Chiba Prefecture, about two-thirds of the way from Tokyo to Narita. You can get there in a 20 minute walk from Keisei-Sakura station.
It’s an expansive museum with an excellent English audio guide. Give yourself at least 2-3 hours there. I had a great time, but if you don’t want to take my word for it, it has a 4.5 rating on TripAdvisor and a 4.4 rating on Google.
The museum’s English website: http://www.rekihaku.ac.jp/english/