Here is an article about Yawatahama Kuroyu Onsen Minatoyu:
Located just a few steps from the port of Yawatahama in Ehime Prefecture, Minatoyu hot springs offer a relaxing and revitalizing experience along the shores of the Seto Inland Sea. This natural hot spring, rich in sodium, meta-silicates, and meta-borates, attracts both locals and travelers in search of tranquility.
Although the water is no longer as dark as it was originally due to the presence of iron, its gentle greenish tint does not diminish its invigorating properties. The indoor baths even have water beds for total immersion in a soothing cocoon. A sauna is also available for lovers of dry heat.
With its wide opening hours until 11 PM, Minatoyu is the ideal place to relax before boarding a ferry. After shopping at the nearby michi-no-eki, there's nothing like a good hot bath to relax before the crossing.
Easily accessible from National Route 317, the establishment is located a stone's throw from the bustling port of Yawatahama, where you can taste the famous marine specialties of the region. A stopover that combines soothing hot springs and immersion in local culinary traditions perfectly.
Whether you are a regular onsen visitor or just curious, a visit to Minatoyu will warm your body and soul in this warm maritime city of Ehime.