http://www.mangago.me/read-manga/yatteraneeze/
+sequel: Halfmoon Emotion
This list is by Mion: http://www.mangago.me/home/mangalist/1759/
yaoi
http://www.mangago.me/read-manga/gokujou_no_koibito/
http://www.mangago.me/read-manga/saa_koi_ni_ochitamae/
http://www.mangago.me/read-manga/himegoto_asobi/
http://www.mangago.me/read-manga/passion/
the warui series from Sakuraga Mei:
http://www.mangago.me/home/mangalist/6968/
the series from Fujisaki Kou:
http://www.mangago.me/home/mangalist/7543/
Dear Green series:
http://www.mangago.me/read-manga/dear_green/
http://www.mangago.me/read-manga/dear_green_hitomi_no_ounowa/
shoujo
http://www.mangago.me/read-manga/kanata_kara/
http://www.mangago.me/read-manga/kaichou_wa_maid_sama/
http://www.mangago.me/read-manga/crazy_girl_shin_bia/
http://www.mangago.me/read-manga/anatolia_story/
http://www.mangago.me/read-manga/faster_than_a_kiss/
http://www.mangago.me/read-manga/tokyo_crazy_paradise/
http://www.mangago.me/read-manga/shiawase_kissa_sanchoume/
Long and really good shoujo:
http://www.mangago.me/read-manga/black_bird/
http://www.mangago.me/read-manga/shugo_chara/
http://www.mangago.me/read-manga/kami_chama_karin/
http://www.mangago.me/read-manga/lovely_complex/
http://www.mangago.me/read-manga/moe_kare/
http://www.mangago.me/read-manga/faster_than_a_kiss/
http://www.mangago.me/read-manga/ouran_high_school_host_club/
http://www.mangago.me/read-manga/himegimi_to_sanbiki_no_kemono/
http://www.mangago.me/read-manga/dengeki_daisy/
http://www.mangago.me/read-manga/shinobi_life/ (no tragedy and a happy end).
http://www.mangago.me/read-manga/high_school_debut/
http://www.mangago.me/read-manga/special_a/
http://www.mangago.me/read-manga/kamikaze_kaitou_jeanne/
For Shoujo:
http://www.mangago.me/read-manga/kaichou_wa_maid_sama/
http://www.mangago.me/read-manga/special_a/
For Yaoi:
http://www.mangago.me/read-manga/totally_captivated/
I'm sorry, that's all I remembered but I hoped It helped. ╮( ̄▽ ̄)╭
Any yaoi OR Shoujo manga have long chapters (story) with complete. Thanks!