Indoor recommendations in Tokyo to escape the summer heat?

Hey all, I was wondering if anyone had specific recommendations for their favorite indoor activities in Tokyo. We'll be visiting in August, which is sadly the only time of year we can go currently, and I know the heat is absolutely brutal (we went last year).

We've already done both teamLabs experiences, some character cafes, a baseball game, and Shibuya Sky. All were incredible experiences, don't get me wrong, but I'm looking for other indoor-based sights & activities to fill our time.

Does anyone have anything indoors they particularly enjoyed during their time in Tokyo? It can even be out of the main city centre and not a typical tourist activity. :)