I visited Erinji on a cloudy day in August. The buses were infrequent, so I hired a bicycle from the History Park opposite Enzan station, and cycled off along Shingen Michi to find the 700 year old temple that was once attended by the Takeda clan of Yamanashi. Rain started to fall as I arrived, and I wandered with my umbrella through the almost deserted garden. The temple buildings include an impressive main hall and a graceful pagoda. Even though Erinji is so beautiful and historically significant, it receives few visitors, so you can enjoy the peaceful atmosphere.
(Shingen Michi has several other attractions including Kogakuji and Hokoji, and a History Walk with many lovely old rural buildings.)