NHK is pretty unique, but is there some aspect about it that you're particularly looking for? The emphasis on hikikomori? The psychological issues that the characters face?
Two shows with similarly aged characters that you might try are
Eden of the East and
Yojōhan Shinwa Taikei ("Tatami Galaxy"). For shows with a strong psychological focus you might take a look at
Kuuchuu Buranko ("Trapeze") and
Ghost Hound.