Just a heads up, but this is the first (and probably only; edit - not anymore) review I'll ever type, so expect bad points, poor explanations, and some minor spoilers. The review is for the whole show, not just season 1.
TL;DR:
Fruits Basket greets the viewer with a warm welcome in the form of a cute slice-of-life romance, but quickly takes that away by making a sharp turn into an emotional story about characters with dark backgrounds, including but not limited to: childhood traumas, abusive relationships, unhealthy family bonds, and so on; however, these backgrounds aren't the only thing going for the characters, as it only adds to the great character writing, making it even better. It also allows for a great antagonist, whose behavior and reasons are easily understandable when the whole picture is formed. Of course, that's not the only thing going for the show; as you may have noticed, a comedy tag is applied - and indeed, the show has a significant comedy aspect mixed in perfectly to make the viewer's mood swing "just right". The Romance tag is also a perfect fit, as this show has a great and serious romance aspect. There's really nothing more the viewer could ask for.
The anime greets you with, at first look, a bright person - Tohru Honda - who doesn't seem to be bothered by the complications in her life and doesn't seem to have any problems at all, like most simple protagonists in such shows. Well, you'd be wrong to think so, because it's just a tough front she's putting up after all her struggles. And even that doesn't last long. With that, Fruits Basket makes its first welcome.
This anime really tricks you into thinking it's a simple slice-of-life show, but don't be so quick to drop it, because it will slowly start to reveal its true colors the deeper you go into it. And the deeper you go, the deeper the story goes. The writing won't let you get bored that easily, as there are new things in every episode, so you're in for a treat either way. For now, just enjoy the show and appreciate the little details (if you can spot them).
If I had to explain why Fruits Basket starts slow, I'd probably say that you want to be familiar with how the characters are now, before you get to know their backgrounds. Once you're familiar with characters as they are currently, you're likely ready to find out their experiences to shape the whole puzzle of their personality. The backstories of each character differ - some were convinced from early childhood that they would end up alone, having them rely on the only bonds that (they think) keep others together with them; some regret not being there for their loved ones; some suffer from not letting the past go; some suffer from not letting their long-gone feelings go, and so on. Even if you don't feel any pity for the character, it'll surely give you all the answers to the questions you might have had about certain characters, be it a "Why are they acting like this?" kind of question or a "Does this quirk of theirs have some backstory?" kind.
Since I already went out of my way to mention that the show includes traumas and feelings/bonds you can't let go of, I really want to give it a special mention, as Fruits Basket gives it much better attention than many other shows. Oftentimes, I'd see trauma portrayed as something that can just be gone in a single chit-chat and never come back. That's honestly not how it works, and FB does it precisely the way it should be done. A dialogue with someone you care about might calm you down, but the trauma will come back to bite you the moment someone or something reminds you of it until you completely let it go. The same can be said for love feelings. It appears suddenly, and you can try to entertain it, but when you have to let it go - it gets painful to move on. So, if you have experienced either, I'm sure you'll be able to relate to some of it when watching this show.
Have you ever felt lonely, especially being afraid to lose the only thing that keeps you in touch with someone? If so, maybe this show could be relatable to you and, perhaps, help you deal with your problems in that regard. I won't go into details, but this show portrays those two feelings quite well, and not only is it embracing them, but it also shows that you'll never be alone even if you let something go - be it some unnecessary bond or your long lost love feelings. If you find these relatable, you will definitely appreciate the anime in the long run.
Don't you think we've been only talking about sad things so far? As much as this anime might make you sad, you'll be sure to remember the bright moments that consistently make you smile regardless of what was happening before. The comedy blends in very well, without being overly annoying and has a little bit of truth to it; jokes aren't overused and are kept in reasonable amounts. Speaking of myself, I probably miss the bright aura of the anime more than the sad one due to the characters feeling 'real,' and their humor plays a big part in it.
Characters feel real. Until this point, I've been mentioning how the character writing is great, their personalities are perfectly understandable, how they have explainable feelings, and so on. But, truly, what does make a character feel real? The fact you met a similar person in real life? Them having the same thoughts you might have had someday? Understanding the chain of thought? Honestly, all of those are correct. If you can even relate to a fictional character, I feel like that makes them real. But what I genuinely want to give a special mention to, is the fact it's consistent; it's not just one thought or one dialogue; the characters as a whole are consistently written in a way that makes them feel real. And what's even better is that there are not just one or two types of personalities. Just as much as there's a variety of fruits in a basket, there's a wide variety of people's personalities, and this show portrays that very well.
What else could make a character feel real? The romance aspect. Pretty much everybody has experienced feelings for someone at some point, and a lot of people have their own ways of expressing love - some are just overly protective about their partner; others like to support them mentally; some make do with just hugging and cuddling all the time. There's no right or wrong way to love somebody(as long as both partners are satisfied, of course) - and, again, Fruits Basket nails that too. The show naturally includes romance in it, but not just simply, as it portrays many different kinds of love very well. Not everything can be perfect either and sometimes, people just go their separate ways - it's unfortunate, it's sad, but that's just how life is. So if you ever felt like you still didn't move on from that and need a little emotional push, or thinking about trying to make things work again, consider watching this show as well, as it may help you on your journey of figuring things out.
The last thing I'm going to mention is the soundtrack - it's simply great. I wouldn't say it's necessarily complex, but it does a brilliant job of accompanying scenes with corresponding moods. Whenever there's a sad, happy, or bittersweet scene, the soundtrack will make sure to fit 'just right' - without necessarily taking the mood over. Listening to the OST again after finishing the show will remind you of all the moments that are associate with played soundtrack; some of them just overflow me with emotions or, instead, make me shiver. That's how you know the soundtrack did its job well. You don't just remember the scenes or the soundtrack separately - you remember them both.
And with this, I'm going to end this review. I don't have much else to say other than just please watch the show yourself - I don't have enough words to express my love for this anime. One more thing I can't fit into any paragraph is that it has a brilliant conclusion to the story in the shape of Final Season; it answers all remaining questions completely and concludes the story perfectly. I honestly can't recommend Fruits Basket enough to anybody who likes the genres even remotely.
~~~If you have any major complaints about my review, feel free to message me because this is honestly the first time I have taken reviewing seriously.