By train
JR Iwaizumi Line serves Iwaizumi from Moichi, the transit station for JR Yamada Line links Morioka and Miyako. However it is extremely infrequent 3 times a day, 1 in AM, 2 in PM and unless you really are train lovers, it is very difficult to negotiate. Japan Rail Pass is accepted.
If you are on the Sanriku Coast, Sanriku Railway does have a station in the east edge of Iwaizumi Town. Omoto Station is 40 mins away from Miyako 750 yen single. The town council operates shuttle bus service from Omoto into Town via Ryusendo Cave 600 yen single usually connect train arrival times.
By bus
JR Tohoku Bus Co. operates a direct bus service 4 times daily from Morioka Station to Ryusendo Cave via Iwaizumi Town Center. The journey takes 2hrs 10mins. Japan Rail Pass is accepted on this bus service.
Morioka Station - Ryusendo via Iwaizumi, daily, ¥2590
From Morioka Station 09:40, 12:40, 14:40, 17:40
From Ryusendo 05:55, 08:55, 13:30, 16:00
The bus leaves from Morioka Eastside Bus Terminal, Bus Stop No.1. No toilet on the bus, but there's a break at the Mitakai SA along the way. All buses go via Iwaizumi Sanbonmatsu. 8 mins before Ryusendo arrival.
By car
Another option is to hire a rental car at Morioka station. Driving in this region is less stressful than in cities like Tokyo. National Road 455 is the shortest route from Morioka, passing through picturesque Gando-ko and Sotoyama lakes. Since the new tunnel through Hayasaka Plateau was completed, the journey time has been cut -- Morioka to Iwaizumi takes around 90 minutes. In the winter, driving times are often longer and conditions are often less safe.