Tokyo National Museum’s regular exhibitions are free to the public on the third Monday of September, the Respect for the Aged Day national holiday. This is one of only two days of the year that you can get in for free – the other being International Museum Day – so it’s worth noting in your cheapo calendar.
The museum exhibits around 600 works of art in fields such as painting, calligraphy, sculpture, and archaeology. Samurai fans should note that they also have arms and armour. See the museum’s website in the link above for a full breakdown of what is on display at any time.
Last admission is 30 minutes before closing: 4:30pm.