After reading several reviews of this anime, I have realized that there is a very important confusion about the work.
Most people say that it is a "Harem" anime, even that it is the pinnacle of that genre. Now, although it is true that it technically meets the characteristics to be in that genre (a boy and many girls in love with him), the reality is that this work is different.
The 100 Girlfriends Who Really, Really, Really, Really, Really Love You is actually an anime that talks about "Polyamory." I don't know if it is the first anime to do it in a serious way (there are so many animes that it is impossible to see them all), but it must be one of the first, and it does it very well.
We are not facing a protagonist who "likes all of them", but one who, in addition to loving them, also all of them, are "the love of his life."
An additional fact, and not easily seen, is that the rest of the girls join this love and all love this polyamorous family. It is true that in other anime like The Testament of Sister New Devil even all the girls marry the protagonist. But it is different.
The key point is that in most harem anime, there is a competition between the girls, because, deep down, they all want to be the only one.
This does not happen here. Here all the girls are comfortable with the protagonist, not only do they like other women, but they also love them as much as they do. In fact, they promote this action by calling it "a family." This great difference is something incredibly original and that gives the plot a spirit of rebellion, morbidity and pleasure rarely seen in any anime of any genre.
Dear reader, when you see this anime (because I recommend it), you will realize that I am right.
Finally, there is another aspect to clarify, and that is the irreverent and spicy comedy. It is an ecchi anime where it is not only about showing fan service (which is not excessive, but very rewarding for those of us who love the genre), but also entering into erotic and spicy situations so sensual and intelligent that you will not know whether to laugh or not.
As a negative point, and even understanding that this work was made to be an eternal manga and a 2-season anime, I must say that 100 girlfriends is too much.
It is simply imperative for any narrative and plot. It is unsustainable. It would be better to dedicate yourself to exploiting polyamory with a more reasonable number (for example, 10). The feeling is that there are so many, that sooner or later the connection between the girls will be lost and the magic that makes this work beautiful will end.
THE GOOD. An original work, really original that talks about polyamory in an intelligent and funny way.
THE BAD. It's okay to want to eat the world, but 100? That's a bad joke.
SPEECHLESS. That's how the spicy moments will leave you. They reach the limit!