If you haven't read them already junjou romantica and sekaiichi hatsukoi are a must. Also these are both really good:
http://www.mangago.zone/read-manga/elektel_delusion/
http://www.mangago.zone/read-manga/hidoku_shinaide/
I've read them all,but thank you very much for you recommendations! ヾ(☆▽☆)
Yes i have,they are really amazing,but i feel like i've read all the best ones so now it's hard to find another (〜 ̄△ ̄)〜
Try this one, its sweet. :3
http://www.mangago.zone/read-manga/koi_to_wa_yobenai/
these are all my favorites ~
http://www.mangago.zone/read-manga/genwaku_no_kodou/
http://www.mangago.zone/read-manga/koori_no_mamono_no_monogatari/
http://www.mangago.zone/read-manga/switch/
http://www.mangago.zone/read-manga/innocent_bird/
http://www.mangago.zone/read-manga/bukiyou_na_silent/
and anything by morimoto shuu is really great! ヾ(❀╹◡╹)ノ~
Excuse me,can someone recommend me some long Yaoi/Shounen-ai manga that is sweet and cute,and it's focus on one couple only (I don't really like multiple stories because it's too short and lack of storyline (づ ̄ ³ ̄)づ).Thank you very much!!!