Naruto Athletic Complex
Address:
Naruto, Tokushima, Japan
Category: Indoor Activities
This place is just off the 28. After you turn off the 11 and head into Naruto via the main city route, all you need to do is follow the signs to the 'Naruto Athletic Complex'.
This complex has a full indoor gym, as well as (my favourite) a small artificial climbing wall. If you've brought your own ropes and harnesses, it only costs ¥200 for admission (to use the climbing wall as well as the gym). I'm not sure if you're able to rent these things there.
If you want to use the excercise gym, you need to first sign up for an orientation, which costs ¥1400.