One thing to note: the series doesn't start at the beginning of the manga -- so there's a bit of backstory that's not told, but in flashbacks and by off-hand remarks from the characters, you get a good idea of what went before.
Main character is Shuichi, a shy and quiet boy. He is pretty cute, and he would rather be a girl. He dresses up as a girl (using a long-haired wig) sometimes, and walks around town like that -- nobody sees that he is actually a boy. Yoshino has the exact opposite: she is a tall girl with short hair, who would rather be a boy and wear trousers. In the past, Shuichi confessed to Yoshino, but she turned him down. They have a friend Saori, who has a crush on Shuichi, and who loans him her dresses.
And then the series starts, with them entering middle school. The series documents those awkward two years, when you're not a child anymore but also not a teenager -- the years where you have to get to grips with your gender and what that means for your sexual identity.
The love triangle between Shuichi, Yoshino and Saori is the main driver in the first half. Saori is quite straight-forward and has a bit of an unpleasant character: she gives her honest opinion, even when that opinion is about someone who is standing next to her. She and Shuichi write a gender-bender play for the school cultural festival.
The second part is about how Yoshino one day decides to wear a boy's uniform to school -- and while that makes waves, it doesn't seem to bother people too much. And then one day, Shuichi decides to wear a girl's uniform to school -- and they take him to the nurse's office and have his mother come collect him... (Because everybody knows that wanting to be like a boy is cool, but wanting to be like a girl is a sign that something's serious wrong with you!)
But Shuichi shows himself to be a very strong character. He always says what he wants and feels, which means he even manages to have one of his sister's model friends as girlfriend (who even dresses him up as a girl and goes out with him). He makes his own choices, and though he is sensitive to how people react to that -- he does keep making his own choices. And that makes the series end on a high note: yes, his body is changing, he does grow taller, but he is who he is, and he decides to make the most of that, in the way that he wants. That's a pretty powerful message to send.
The animation looks like every frame is a small watercolor painting, which complements the story quite well. The voice acting is superb. The characters are well-drawn, and with clothing being important to the plot, there's lot of attention to the outfits they wear -- not always wearing the same thing.
- Very honest treatment of a difficult subject;
- Looks gorgeous;
- Never boring;
- Ends well.
I can't think of any bad points. I highly recommend this: I'll give it a 9.5.