Chusonji is a temple in Hiraizumi, Iwate which is listed on UNESCO World Heritage.
Hiraizumi was a seat for clan called Oushu-Fujiwara which ruled the norther Honshu in the middle age.
Chusonji has a golden small temple called Konjikido which shows the wealth of the Oushu-Fujiwara family.
Hiraizumi station is unfortunately not a Shinkansen station but on Tohoku main line. If you want to travel from Tokyo or Sendai, take Tohoku Shinkansen's Yamabiko train which stops at Ichinoseki station. Ichinoseki is a relatively large city in the southern Iwate., then change to local train of Tohoku main line. It is just two stops from Ichinoseki.
If you want to continue to north after visiting Chusonji, take the local train bound for Morioka, capital of Iwate prefecture. All Tohoku shinkansen trains call at Morioka and you can continue to Akita, Aomori or even north, crossing the Tsugaru strait to Hokkaido.