Henkyou no Ofuroya-san, Harem ni Naru: Yamaoku ni Aru Sabireta Onsen no Kounou ga Cheat Sugite Onna Boukensha ni Daininki na Ken

Deep in the remote mountains, a young man named Rio manages an aging, dilapidated hot spring. Relying on a mysterious skill to adjust the properties of the water, he initially believes his work is entirely ordinary. However, he soon makes a startling discovery: the spring's restorative effects are far beyond normal, possessing cheat-level power capable of not only healing injuries but also significantly strengthening those who bathe in it. Word of this miraculous bathhouse spreads rapidly throughout the region, drawing female adventurers from all walks of life who flock to the secluded mountain retreat seeking its extraordinary benefits. Yet, the spring harbors an unexpected complication that goes far beyond simple physical enhancement. The potent waters do more than just mend wounds and boost strength; they awaken intense, hidden desires within those who soak in them. As the influx of powerful women continues to grow, Rio finds himself at the center of increasingly intimate encounters, transforming his quiet, run-down bathhouse into a haven where steamy mixed baths and irresistible attraction become an unavoidable part of daily life.