Semi Onsen Kirinohana Yamabukinohana

Standing alone beside the Natsuyu River in Wagacho Iwasaki Shinden, Kitakami City, Iwate Prefecture, this inn is one of the springs making up the Natsuyu Kogen Onsen Cluster, alongside Natsuyu Onsen, Irihata Onsen, Suijin Onsen, and Natsuyu Kogen Onsen. A predecessor spring called Semeno Yu once operated here but closed in the early Showa era. Taking up that unfinished dream, Yumi Kikuchi of Ezurikomura village funded a new drilling effort, beginning on the left bank of the Natsuyu River in December 1959; by May 1960 the well, at a depth of 280 meters, was self-flowing at 42.5°C and 99 cubic meters per minute, and drilling continued to 420 meters before the inn opened for business, making it a relatively young hot spring resort. The name Semi Onsen was chosen through a public naming contest, adapting the local place name Semeno into the reading semi.

The water is an alkaline simple hot spring rich in metasilicic acid, with a temperature of 42 to 46°C and a yield of 745 liters per minute. The inn draws on three distinct sources of differing character — Bijin no Yu (Beauty Spring), Yume no Yu (Dream Spring), and Chojyu no Yu (Longevity Spring) — with Bijin no Yu especially prized for its silky, lotion-like texture and faint iron and sulfur aroma, said to leave the skin smooth after bathing. All three sources flow untreated, without dilution, heating, or circulation, and are said to benefit neuralgia, muscle and joint pain, poor circulation, chronic skin conditions, and general fatigue.

The bathing facilities include six indoor baths drawing on the three separate sources, three outdoor baths including one mixed-gender bath, and private family baths, along with guest rooms featuring their own open-air tubs. Nestled among the mountains of the Natsuyu highlands with a mountain stream flowing close by, the inn offers fresh greenery in spring, deep summer foliage, autumn colors, and snowy winter scenery. Day-trip bathing costs 1,200 yen for adults (400 yen for elementary school children, 200 yen for infants, plus a separate 150-yen bathing tax), available from 10:00 to 20:00 (last entry 19:00). As of July 2026, due to wildlife damage, the Chojyu no Yu baths (both indoor and outdoor) are temporarily closed, while Yume no Yu and Bijin no Yu are operating on shortened hours.