Shikoku by car...

We'll be arriving in Tokushima by ferry from Tokyo mid Sept. and hiring a Tocoo car for two days. Would driving to Iya Valley and Kochi and back be feasible with an overnight at Iya Ikeda in that time?
Can anyone suggest a nice route to drive?. We don't mind non-toll smaller roads.

Driving times off the expressways are surprisingly long on Shikoku, especially in the Iya Valley, because roads are narrow and windy. If you start in Tokushima on day 1, I recommend to schedule arrival in Kochi for the afternoon of day two to have enough time for the Iya Valley. I recommend to drive along the entire valley starting at Mt. Tsurugi. I really enjoyed my overnight stay at Iya Onsen:
http://www.iyaonsen.co.jp/english.html

Maps of Shikoku seem rare for some reason - could you kindly indicate an actual driving route suggested from Tokushima and back please?

The Iya Onsen Hotel Uji suggests is fabulous - stay there, perhaps in an upgraded room - private hot-spring overlooking the valley - lovely! For maps I suggest tyou use Google maps. Enter Japan into any country's Google maps then enter Tokushima, then click get directions. You can then enter a place to head for - Iya Valley is a little tricky so try awaikeda, the main station near the valley - that should work. This tells you road numbers, journey time and you can zoom in and see the route on the map.

PS - Dont forget Kotohira, north of Iya. Unless you have a specific thing to see in Kochi I would say Kotohira (with beautiful hillside shrine) is better - depends on taste though!

I'm afraid Awa Ikeda defeated Google maps, but I'll keep trying......