No single answer: Kurokawa's waters, inn by inn

Every inn owns its own source. So the village has no single water, and that is the interesting part.

Why there's no single answer

Water varies inn by inn. Every ryokan owns its own source.

Most onsen towns can answer "what's the water like" in one line; Kurokawa structurally cannot, and saying so is this page's whole value. Each inn drilled or channels its own 源泉, each source carries its own mineral signature, and the spa association's own data sheet lists four registered families across the village — sulfur springs, bicarbonate springs, chloride springs, and sulfate springs. The consequence for bathers is the tegata's secret second function: three stamps buy three chemistries, not just three views. Misato's milky sulfur bath and a clear bicarbonate tub two lanes over are different products from the same hillside.

The designation's map

Zoom out and the plurality is official: Kurokawa anchors the 南小国温泉郷 — the five-hamlet National Recuperation Hot Spring Area (黒川・田の原・満願寺・小田・白川) designated by the Environment Ministry — whose profile registers Kurokawa proper as simple and chloride springs, the middle hamlets as bicarbonate country, and Shirakawa as sulfur. Serious soakers can read the 郷 as a graded menu: gentle simple springs to full sulfur theater inside one bus route.

The seven-of-ten claim, gated

The association's own marketing counts 7 of Japan's 10 official therapeutic spring types across its inns — a claim that lives in the 組合's yumeguri PDF, which our fetch could not read (the site renders by JavaScript). The rule this page keeps: that count prints only after the PDF click-check, phrased as "the association counts 7 of the 10 official types across its inns" — attributed, never measured, and never inflated to "all types." The two spa-association records themselves disagree on the exact list, which is precisely why the gate exists.

What the waters traditionally claim

The published register for the Kurokawa entry runs sulfur-led: traditional 泉質別適応症 for atopic dermatitis, psoriasis, chronic eczema; the general register covers chronic muscle and joint pain, cold sensitivity, circulatory complaints, fatigue and convalescence; 禁忌症 flag sensitive skin and the standard exclusion list. The designation profile adds the per-type texture: sulfur toward skin indications, chloride toward cuts and cold, simple springs toward autonomic instability and sleep. All of it as published — tradition at the door, not medical advice.

Using the map

The river runs warm enough to smoke in January.

The practical version: ask each front desk どんな泉質ですか (what's the spring type?) — inns proud of their source answer in detail; pick your three tegata stamps across families, not within one; rinse after sulfur if your skin runs sensitive; and treat any per-inn pH number you meet online with suspicion — no certificates surfaced in our verification, so neither do numbers here.