Story:
This is a story about subjectiveness, about the different views of different people.

The toxicity is what makes this story great due to it being realistic. And while romanticized toxicity will make you frown in disgust, realistic toxicity will ironically deliver goosebumps because you can't help but find it beautiful through the eyes of the characters.

This manga is also a great study of humanity and society. How do we behave towards something unknown, something shunned by your surrounding which has been brainwashed? Love, friendship, family, homosexuality, misunderstandings, illness, rape, suicide.
So many sides of society are shown, so many kinds of people are introduced.
How should we behave in such a society? How do we behave in regard to each other, in a place where everybody is so different?

And why is it that despite the passing of time, some things remain unchanged? You can recognise so many problems (although subjective) from a time so long ago, in today's society.

Let Dai doesn't answer these questions. It makes you think about them.
For years (cause I used to re-read this every year) I couldn't grasp why this story is so beautiful. I thought that it was because I liked dark, psychological stuff and tragedy.
That's partly true, but now I finally understand that what truly defines its beauty is how awfully realistic and relatable it is.
It is so beautiful because it carries such a heavy yet subtle message, while taking you on the journey of two flawed boys, living in a world so unfamiliar yet known.

Characters:
Another outstanding point is the character study. The side characters are really deep with each their own stories, and the main characters are even more complex. There are people whom you won't be able to understand in real life. But now you do because you've crawled into their skin and experienced what they have experienced.
They aren't heroes or good examples you should take notes from. They are your everyday people, and that's what makes them so complex.

Art:
The art is stunning. Considering the fact that the manga is pretty old now, the art style can be said to be "outdated" so you'll have to get used to it. Despite is being outdated, it's still very beautiful. It's an art style of its own.