When it comes to harem anime, reviews like these are often taken with a huge helping of salt because of the nature of these animes. However, Gotoubun no Hanayome is, dare I say, the pinnacle of harem anime, featuring the most rounded cast to have ever graced this genre, a sufficiently detailed and well-established storyline, and, surprisingly, not a lot of ecchi, which is definitely refreshing at that.

Story
The overall story isn't that outlandish, a financially struggling straight-A high school student gets offered a job to teach 5 wealthy quintuplets, from there, one by one, the quintuplets fall to the high school student's charm and eventually all compete for his love. It's not something we haven't seen before, and BokuBen used this style earlier this year. However, where BokuBen slows down, this anime speeds up. We are given a Nisekoi-Esque promise from 5 years ago to help solidify the protagonist's relationship with the 5 girls and each girl's individual arcs puts her on a shining spotlight in a unique way, allowing for equal development in both her strengths and her weaknesses. While other anime tend to cloud these developments with the girl's innate desire to fall in love with the protagonists, this anime uses that motivation, or in Nino's case, the lack of that desire to develop their personality. The result is a very diverse cast that almost feel real, so real in fact, that I feel a much stronger connection to these girls than any of the other anime I mentioned before.

Art and Sound
The art featured in this anime is varied, to say the least. It decreases in quality when it needs to and increases whenever possible. I find that this is shown most in a simple comparison between the quintuplets' penthouse and Uesugi's room, one comparison shows so many subtle details the artists added in to heighten the girls' development even more. Don't even get me started on the festival arc. Not only is the lighting and art at every individual firework spot-on, the way the lighting interacts with each girl to set certain moods is effective as well.
Regarding sound, the OST makes a good job of highlighting each girl's personality in their own respective arcs, as well as easily set and maintain moods during arcs such as the Summer Camp Arc and the Festival Arc. The OP and second ED are great too, with each quintuplet's VA pulling their weight to the max to deliver this upbeat OP and soothing ED that I can't help but listen too, even after finishing the show.

Characters
As I mentioned before, I think the cast of Gotoubun is the most rounded I've ever seen in a harem anime. For once, our protagonist Uesugi isn't as dense as a neutron star, and can actually notice and understand each girl's feelings as the anime progresses. It doesn't mean he's completely out of the park yet, as he is still hilariously dumb when the anime needs him to be, but at least he's not a complete idiot either.
Regarding the quintuplets, each of them embodies a commonly seen trope in anime girls, and uses that basis to develop them into well-rounded characters.
Ichika is your typical onee-san, a bit lewd here and there, but overall the most protective and caring for her sisters, to such a degree that she often keeps many secrets from them just so that she can maintain the quality of their lives. Nino is your typical hard-headed softboiled idiot, she loves her family, but hates outsiders. Like the membrane of a cell she just doesn't let up until you prove to her that you're friendly. While the anime didn't cover the chapter that converted a good portion of the fanbase, Nino still saw enough screentime for us to glimpse at her inner feelings and feel hype for her inevitable development in Season 2.
Miku is my personal favorite. Shy, booksmart, and from her family's standpoint, the smartest of the bunch. The anime immediately capitalizes on her at the start of the series, solidifying her as a force to be reckoned with for the remainder of the series and well into the manga. She's the first to show her soft side to Uesugi, and by doing so establishes such high of a character to place her firmly as my favorite best girl.
Yotsuba is your muscle-brained nice girl. So nice that she goes out of her way to help. While the anime (or the manga, for that matter) didn't cover much for her development, she's made it clear that ultimately, she exists to support people, which is why she goes out of her way to help places like the sports teams in the anime. She wants her sisters to be happy, and by doing so she sacrifices her own happiness for them. A kindhearted soul at that.
Itsuki, in my opinion, received the least attention, she's established herself as a semi-tsundere food lover at the start, and that's it. She didn't receive much development after that. But whatever development she did get did solidify her enough so that she can stand on her own. Hoping to see more development for her in Season 2.

Overall, Gotoubun gave me a stunning example that not all harem anime has to be super ecchi and devoid of character development. Each character felt stunningly real and well-developed, and I'm definitely curious to see what the next season could bring for them