Sex, sex and sex. Only thing that contains this manga is all about sex. There's a razor thin margin between hentai and this manga. Or you can say there's no difference between highly censored hentai manga and Koibana Onsen. No strong story line, just some random stuff about Onsen customers and blah blah blah. I like to read ecchi & matured theme manga but only with one condition, there have to be drama and some ups and downs in relationship. So I thought I'd give it a try. This manga seemed to me a river without flow. Just moving forward without ups and downs and just full of sexual contents, nothing more.
The story starts when Akiyama Kazuhiro the main male lead came to Koibana Onsen alone with a heart break. Koibana Onsen is actually for couples, so when the Nonohara sisters who run the Koibana Onsen founnd out about his problem they decided to help him. And so when they almost made it and bring Akiyama and her girlfriend together Akiyama suprisingly confessed his love of Nonoka to his girlfriend. So their relationship ended their and Akiyama decided to win over Nonoka. That's why he started as a part timer in Koibana Onsen. There was no hindrance or upside down thrill in their relationship. They easily fall for each other without any drama or what so ever. So I didn't find any strong plot or any thing.
Though some might enjoy the relationship of Rurika and Shuuhei couple. But personally I prefer Fuuka's background story. And about Moeka X Gin couple really pissed me off. Other than these the story is covered with strange couples and thier weird acts. So I'll give it 5 out of 10.
Not so good and not so bad either. Sometimes some face expression was horrible but Nonoka's expression compensate those horrible arts. Some face expression off Akiyama really pissed me off. Only three Nonohara sisters' character art and background art are what I liked. I'll give 5 out of 10.
Character's characterstics can be better when the story line is good. So there's nothing much to talk about. But one thing for sure if there was no character like Fuuka the story could have been more boring. She is the only reason so that anyone can count it as a comedy manga. Nonoka is beautiful and good wife type, Moeka is clumsy type, Rurika is what you can call Tsundere but lowest of the low Tsundere I'd say. There's nothing much to talk abou Akiyama! But he's the main character! Gimme a break. Shuuhei and Gin they are the quite opposite if you count their size, but both of them are not manly man GUHHHH... I'll give 6 out of 10 only for Nonohara sisters.
Overall I'll give 5.5 out of 10. I lost my interest while I was in chapter 30 but still I was able to read it to the end and felt all I did was just waste my time. In the beginning I really liked it but the story ended without any surprise or any interesting event. This one is not that type of manga which will hit you or make you think about it over and over. This is just an average harem, ecchi manga without potential. Personally I didn't like it and I won't recommend it. But if you are obessed about only passonate sex and stuff then you can try this one.