To be honest I waited quiet a while before writing this review because it's completely: 1-to get over it, 2- to only point out some things. So here is my confused review that can't express half of what I could say:

First, the story is about so much more than love. Their is friendship of course, with a group of friends I really laughed with with all their adventures and stories;
the passion of the main character for her sport and the tension they could create in matches, we felt her passion, her despair, her pure joy, she lived her sport and we lived through her, being excited and anxious with her;
the feel of the 80-90's period and all the historical events being brought up, really adding something. We can feel the world changing and the characters growing with it, a coming-of age story where we see the evolution and different path the chance can push you to take, it was both refreshing and melancholic in a certain way.
Also of course (but I'll still say it) all of the characters were so lovable and everything kept you interested. It's not one of those drama were you only wait for the characters you like to get screen time, nor one of those were the second lead is only here to revitalize the story when the lead couple becomes boring, no. Here, at least for me, all the characters had something to add and we were happy to see all of them on screen. They also had a good development so we were watching them live and accomplish, not only be the same with an objective that had to fulfill (being the best friend, having a heartbreak, being poor, things like that that doesn't define a person but are sometimes used as the sole characterization of characters)
Do I need to say the chemistry was perfect and the moments between the leads both cute and funny? Well they were, and the main reason is because it is slow burn. REAL slow burn. Meaning they don't have a reason to be together and fake their live until they make it. Here it's more about getting to know each other perfectly, feeling fluttery bit by bit then this sensations growing into live, the love kept secret, etc, all the steps for the spectator to really enjoy every bit of their story. After getting really close and even after becoming a couple, it didn't become flat and lose the cuteness of the beginning. I followed every step with the up most attention and investment. They unquestionably became one of my favourite couple.
However, even though I found the end obviously good and even poetic in a certain aspect it broke me. I was so moved after finishing the series because I was so invested in it. I really feel like I watched something great and I have this emptiness not only from having finished a series I love and missing the feels and atmosphere but also the quite realistic anxiety that I may not feel so much with other drama because 25 21 was objectively incredibly good.
(Well I ended up writing a lot haha)
Anyway if you haven't had a chance yet or hesitate to watch it, do it. You will not regret it :)