Ryokan Ohnuma is a traditional hot spring inn with over 120 years of history located in the Naruko Onsen area of Osaki City, Miyagi Prefecture. Situated in the Higashi-Naruko Onsen district within the historic Naruko Onsen town, which boasts 1,200 years of hot spring heritage, this inn is a member of the Japanese Association of Secluded Hot Spring Inns. It is conveniently located about a 5-minute walk from JR Rikuu East Line's Naruko-Gotenyu Station. The greatest feature of Ryokan Ohnuma is the ability to enjoy eight distinctive baths using two different types of sodium bicarbonate springs. The self-owned source "Ohnuma no Yu" is a pure sodium bicarbonate spring with pH 7.0 (neutral), a precious source that has been used since the ryokan's founding. The other shared community source "Karatake no Yu" is a sodium bicarbonate-chloride spring with pH 7.4 (slightly alkaline), characterized by high heat retention and coating effects due to its salt content. Both sources contain minerals from ancient plant fossil layers and are rich in metasilicic acid, making them highly effective for skin beautification. Of the eight baths, five can be used as private baths free of charge, with no reservation needed - guests can simply use them when available. The large bath "Yakushi Sennin-buro" is mixed-gender but has designated women-only hours. There is also a women-only bath "Tennyo-buro." The three free private baths are "Kage no Yu," "Yo no Yu," and "Akari no Yu." "Fukashi-buro" is an aromatic steam bath used while clothed. The premium private garden open-air bath "Mori no Yu" is available for an additional fee and is extremely popular. The inner garden open-air bath "Ishiwari no Yu" can also be enjoyed as a foot bath but is closed in winter. All baths use 100% natural flowing hot spring water without any added water, circulation filtration, disinfection, or bath additives. The hot springs are beneficial for neuralgia, muscle pain, joint pain, chronic digestive disorders, poor circulation, fatigue recovery, and skin beautification. Ryokan Ohnuma promotes the modern toji (hot spring therapy) experience, recommending stays of 2-3 nights or longer for full relaxation. Accommodation includes the main ryokan building with full-board plans and the toji building offering room-only or self-catering options. The cuisine using local ingredients is highly regarded, and various stay styles are offered including workation plans and fasting plans. Day-trip bathing is available for 500 yen for adults. The inn is known for the fifth-generation hot spring keeper's dedication to spring management and warm, family-like hospitality.