Green Green Greens is easily the best sports manga I have ever read.
This story is incredibly bold in it's premise, that being the mindset shift of a teenage boy becoming an adult and having to find what is precious and what is worthwhile for him. It's a story about doing what you love and loving what you do.
Characters are charismatic and the protagonists, specially, are deep enough to have good arcs without taking from the simplicity that makes it so easy to love them in the first place.
The story does exactly what it proposes itself to do. Even though it was super short, it ended up not feeling incomplete at all. It is so common for these axed mangas to have bad endings, but in the case of Green Green Greens, it seemed incredibly natural. From beginning to end, this story is incredibly moving and is also able to express aspects of athlete mentality like I've never seen.
Tl;dr: perfect and self-contained story about personal growth and mental maturity. Couldn't recommend it more.