This is a character-centric harem comedy ecchi. Everything from the premise, the setting and the shallow, largely episodic plot points are just an excuse to further the basic outline of the MC building out a harem one girl (usually) at a time. If you are expecting to follow a volleyball sports manga with some ecchi and fan service in between intense tournament drama then you have found the wrong title.
You can't and shouldn't take this manga seriously and there is every indication that the author doesn't expect you to. The idea that these amazons would be tripping over themselves chasing after this dorky MC as if he was the last guy on earth or something is ridiculous on it's face and how the MC handles it all is equally ridiculous and unbelievable. Almost all of the characters are some form or another of absurd deviant caricature with some being notably more outrageous than others. Each of their personalities are fairly distinct and consistent within themselves and the girls all play off of each other well in most cases. The most normal or sane characters you are going to get here are probably the volleyball team captain, her bedridden father who seems to be in good health for someone apparently living out of a hospital and the captain of the basketball team that the main cast frequently run into and proceed to antagonize.
But what this manga does well is that it is fairly entertaining and totally unapologetic. You can't help but be amazed at the stupidity of the scenarios and the sheer insolence of the author for writing this in the way they did. Some chapters are definitely better and more memorable than others and the ones that center around college volleyball, though few and far between at times, are some of the better and slightly more serious ones.
The art is quite good in my opinion. The body types on display here are obviously a bit over the top as the title suggests but the character designs are very much "S-tier" and from what ensues you can tell the author is having fun drawing this.
The elephant in the room is that this guy (MC) is probably going on too many, as they refer to it in the manga, "dates", with his sister and it's largely played off as quirky, racy or some kind of normal-adjacent. What is there to say. The author's obsession with this particular pairing over all the other pairings in this harem that one could push from a character development standpoint is somewhat frustrating however in the end and as mentioned earlier this is not a manga to be taken seriously, even by ecchi standards. The idea that this guy would score with any of these girls is already stretching believability and scoring with all of them repeatedly and regularly.. would never happen. So with this pairing you don't exactly have to suspend your disbelief that much more than you already are. Part of the formula here is in the utter madness of it all.
As of chapter 77, despite the gradual escalation of degeneracy the manga is fairly consistent overall and is generally rude, lewd and amusing.