Open air onsen - Done! Sat in an open air onsen along the Kumano Kodo and got my butt bitten by a vicious butt-biting fly of some kind. It was spectacular.
Sumo wrestling - apparently it's only on sometimes during the year but the wrestlers train year round so if we miss the tournaments, we can go and see a training session (dad says that the wrestlers like to bench press Western tourists to show off for photos). Also, the training centres are called stables rather than gyms! Experience of sitting ring side at a sumo tournament: "Ticket holders sit on cushions on the floor and are exposed to the risk of injury due to wrestlers flying into the spectators."
Edo-Tokyo Museum - museum looking at the Edo period (1603 - 1863) - Done!