Izukyu line pass vs Tokai bus pass

Which one you should get depends on which area of Izu you’ll be visiting. The train runs only down the outer edges of the Izu Peninsula. If you're planning to visit these parts only, then use the Izukyu Line pass (for trains only). But there are places to see in the middle of the peninsula too, so if you're going to visit the middle part, then the only mode of transport would be the bus. So you should get the Tokai Bus Pass.

Izukyu Line One Day Pass http://www.izukyu.co.jp/global_site/pdf/onedaypass_4.pdf

Tokai Bus http://www.tokaibus.jp/file.jsp?id=8582