Koibana Onsen is a reminder that while filler sucks in anime, it can be quite awesome in ecchi. Set at a mountain onsen bath, every chapter brings new characters, which means a constant flow of new girls getting naked, with nudity in every single chapter so far.
It doesn’t take long before some tasteful sex scenes enter the fray as well. Most chapters are non-essential to the plot- they’re a flimsy excuse to show the next set of awesome boobs.
This revolving door aspect to Koibana Onsen is actually pretty ingenious- seeing a constant flow of new girls and new situations keeps the fanservice from getting stale. And though we don’t get teased all that much and the fanservice and sex both feel rushed, for whatever reason this adult ecchi manga still pleases.
Koibana Onsen manga (first two volumes, ongoing)
Though the pacing and themes of this manga come dangerously close to wandering into hentai territory, it at least attempts to inject some actual love into these lovemaking sessions, and the series actually ends with a white wedding (and of course the post wedding sex scene).
I don’t know why, but I really liked the character design in this and the nudity is drawn pretty well too. Usually manga this low on tease isn’t all that much fun, but for whatever reason, Koibana Onsen’s relentless fanservice assault does the trick.