If you stop at Ito, then you can catch the bus to Izu-Kogen. This is the cheapest way. If you arrive Izu-Kogen station, from there you can catch Taxi to Puppenhaus. It will cost you about 2000yen. There are few buses to Puppenhaus.
Bus schedule is here .
If you come by car, take Izu-Skyline road till the last toll gate and 3km after the exit on the right is the Puppenhaus.