BTW, there is a joke embedded onto the name of the bathhouse, and it requires some explanation as to the wacky name, why Tsukasa thought it was aggressive and why the disclaimers are supposed to be funny. So the name of the bathhouse is:
Kusatsu onsen-fu Yufuin 草津溫泉風湯布院 or roughly “Kusatsu onsen Style Yufuin”. So it’s a bathhouse named after Yufuin that do their baths in the same style as Kusatsu onsen.
Kusatsu 草津 is an onsen resort town halfway between Tokyo and Nagano in Gunma prefecture up the foothills of the Japanese alps - it’s known for the scenic beauty of its surroundings and the supposed tonic qualities of the water - their chamber of commerce will in fact hammer those supposed qualities to anyone within their earshot. Nasa and Tsukasa will later take a train (Kusatsu-Shima express) to the actual Kusatsu Onsen resort as part of their honeymoon.
Yufuin 湯布院 is a similar resort town in Oita, Southeastern Kyushu, a region known for having some of the hottest temps in Japan off their local hot springs and supposedly loaded with invigorating minerals throughout (oh, their chambers or commerce are just as pushy as the ones for Kusatsu).
The fact that the disclaimer says “yeah, nothing special or medical here, we use regular tap water, in fact we chlorinate it” makes the name ridiculous since it references 2 of Japan’s more famous and supposedly magical/healing hot springs resorts. Looks like Viz downgraded the joke with the name “the bestest most famous baths ever” in the official translation and kept the disclaimers. Still a good chuckle, but you’ll end up wondering why it’s there in the first place.