I've watched a lot of sad animes like bannana fish, your lie in April, your name, tokyo magnitude 8.0, a silent voice, plastic memories, violet evergarden, angel beats. But i am a heartless bi*ch and will laugh at their misery...........
^ It doesn't take 10 episodes, but the first few episodes are about the Nana's meeting and getting thrown together. Nana is one of the rare, non-magical girl, non-school shoujo anime that has lots of episodes (47).