I went here a long time ago. I wanted to go to Minatoyama Onsen, but it was closed. Remembering that I had seen this sento from the No. 7 bus on the way, I walked back to it. Aioi-Yu is small. Very small. That didn't bother me, however. Although there wasn't much as far as baths, the character of the place made up for it. After getting out, I chatted with the grandfatherly owner as I drank one of the retro bottled sodas that sento only seem to sell.

Update December 2019:
Accessible from a small alleyway heading off the major road that parallels the mountains that contain downtown Kobe city. It is best to get here by taking the #7 bus up the hill. This is a small little sento with only three baths. The shallow and deep baths are terraced while a small jet bath has a few lemons in it to make it a bit different. It's a small place but it has a big heart. If you happen to be in the area I would recommend heading to this fun little neighborhood bath.