The Oyama Tofu Festival is a little out of the way: a 1-hour train from Shinjuku to Isehara on the Odakyu-Odawara Line. Then you need to catch a 20-minute bus to the festival venue in Oyama. But at the end of the journey is the ultimate tofu eating experience.
Highlights include a Wanko Tofu speed eating contest, which you can watch via the link below. You can even make it yourself, or just buy it as usual in various shops around the festival. There’s also a giant pot, 4 meters in diameter, where you can see (and eat, obviously) the tofu made inside – note this tends to happen quite early.
The event runs from 10am until 4pm on Saturday and from 10am until 3pm on Sunday.