Kimi wa Pet, Paradise Kiss, Skip Beat, Kaichou wa Maid-sama.
Lol none of those protagonists are mature....
http://www.mangago.me/read-manga/paradise_kiss/
http://www.mangago.me/read-manga/cat_street/
http://www.mangago.me/read-manga/and_okazaki_mari/
http://www.mangago.me/read-manga/orange_takano_ichigo/
http://www.mangago.me/read-manga/the_one/
http://www.mangago.me/read-manga/there_s_something_about_sunyool/
http://www.mangago.me/read-manga/kiss_never_cry/
http://www.mangago.me/read-manga/hachimitsu_to_clover/
http://www.mangago.me/read-manga/beck/
http://www.mangago.me/read-manga/karekano/
http://www.mangago.me/read-manga/cat_street/
http://www.mangago.me/read-manga/5_centimeters_per_second/
http://www.mangago.me/read-manga/sakamichi_no_apollon/
Hey guys did you know any manga like NANA?? Especially mature and cool female mc