The origin of the iconic Onsen Mark

Onsen Mark Day (温泉マークの日) is observed on February 22nd. The anniversary was established by the Isobe Onsen Association in Annaka City, Gunma Prefecture. Isobe Onsen is a historic hot‑spring town along the Usui River, long known as a rest stop for travelers on the old Nakasendō route.

The area is famous for being the birthplace of Japan’s oldest onsen symbol: an Edo‑period document from Isobe contains the familiar three‑steam‑line mark. The three-steam-line, pictured below, has become the standard symbol for hot springs. In Japan, there is an emoji for it too. We can't use emoji in our posts, so unfortunately, I can't not show it here, but it looks very like the original three-steam- line mark.

The date, February 22nd, comes from a playful visual interpretation of the three curved steam lines in the onsen mark. When viewed in reverse, each curve resembles the number 2, creating “2‑2‑2.” The association also links the date to three “onsen words” beginning with fu (ふ), for the number 2: 風情 (atmosphere), 風景 (scenery), 風味 (flavor).