I regret I didn't appreciate this drama, but it has completely disappointed me, because initially the plot intrigued me a lot and I think it had potential, but unfortunately it was not used to its full advantage.
Let’s start with the fact that I didn't like most of the characters:
-Nao is absolutely fond of Uehara, always with her head in the clouds that can't notice how toxic their relationship is. Extremely sentimental about everything, exaggerated in reactions, dependent on her boyfriend and always careless.
-on Uehara I don’t even know what to say. Initially I thought he was just a very introverted and reserved person who seems cold on the surface (and being so I understood his character), when in reality even with his friends, relatives and, especially with his girlfriend, he continues to have a detached, cold and (almost) superior attitude. In the relationship he often has toxic attitudes, cuts out Nao from certain situations and almost never communicates. I would call him the typical "perfect guy" that everyone would like to have, but then has a bad temper, simply justified for being too handsome.
-Daichi despite being much sweeter and kinder than Uehara, I still didn’t personally like him (and I say this as a fan of Dori Sakurada). In short I can say that I found him a little too insistent and possessive towards Nao (although I can still accept his jealousy as long-time friend of the girl, considered almost a sister).
-Issei was my favorite. Always respectful of Nao and jealous within the limits of normality. He was always worried that Uehara would make her feel better, instead of wanting to separate them. He has always treated the FL as part of his family and you can see that he cares a lot for her, not just romantically.

The story, in my opinion, could be developed in many less episodes, so as not to make the view so boring. After the first few episodes I got tired more and more, until I couldn't wait to finish the last episode as soon as possible. Despite this there were nice and funny moments, which made the scenes lighter, but beyond that there is not much substance IN MY OPINION.
The happy ending seemed a bit "forced" and rushed, as if all the problems appeared in the previous 16 episodes have been resolved all at once.
I should mention that I found the acting quite poor.
Also I know that this drama is adapter from a manga of the '00, but I can't say that I have appreciated or watched with indifference certain scenes where male characters insistently harassed girls without their permission (for example I remember the scene where Nao is in the hospital and meets Yuu for the first time). I know absolutely that these behaviors should NEVER be done, but I say this because I read comments from people who justified these actions only because they're from a story written about twenty years ago.

Even if I didn't appreciate the first season, I think I'm still gonna give a chance to the second one.
I wouldn't rewatch this drama and I don't feel to recommend it, but of course this, as I repeat, is only MY OPINION.