This will be all my opinion of the Five Main Heroine and If you don't like the Ranking then comment about it.
"Ichika no ecchi"
Okay! let's go to No.1 , "Charles or Charlotte Dunoa" , She the most Cutest or Attractive heroine that get most attention through out 4 Episode that really dominate the series.
"Which look's you like for Charlotte, Male or Female?"
Charlotte was introduce as a male as "Charles"(but I doubt about that)just to spy on Ichika , however not long enough Ichika found out her real Identity (from seeing her in the Shower) that she think her life is over but he decide to protect her and keep it a secret to the Entire school that made her fallen for Ichika.
After the Inter-Tournament she decide to tell Ichika her real name and to show the Entire school that she is girl that really made the other 3 heroine mad at Ichika hehe^^.
Next No.2 , "Houki Shinonono", The first childhood friend of Ichika that was suppose to be No.1 in my rank before Charlotte show up. Houki really in love to Ichika since childhood but she doesn't want to show it or rarely show it because of her pride or just she know how dense is Ichika is. Her voice actress is Yoho Hisaka(the one who voice Mio in K-On).
Anyway for being Ichika's first childhood friend, first room mate and the first girl he saw almost naked after shower that really give her No.1 in my Ranking list, however Charlotte have one thing that Houki or the other Heroine doesn't have, that is a secret between Man and Women ( secret of Ichika and Charlotte) and that for a whole month not knowing to others that simply make Houki No.2 in the rank.
Next No.3 , "Huang Lingyin" or "Rin" for short. She Ichika Second childhood friend and promise to marry her or something like that if Ichika figure out what that means.
She simply the most typical childhood friend that you can see in every anime like Stereo type, Hot Tempered, not very honest and most of all she attack the Protagonist(Ichika) merciless without second thought.Well she have the typical Chinese girl trait(like Shampoo in Ranma 1/2) that only Ichika she interest nothing more to the other heroine.
Next No.4, "Laura Bodewig", The First Heroine to slap Ichika dense carefree attitude to sense in her arrival in IS academy.
Well that really give him the thought that not every girl like him hehe^^
She really likes her Instructor "Chifuyu Orimura", Since she the one that help her overcome her depression however she scent great jealously from Ichika because that what Chifuyu love the most and hated more Ichika because Chifuyu withdraw in the 2nd IS Inter-Tournament not knowing that He was kidnap by that time.
Well there a saying the more you hate, the more you love and Laura show it^^.
Well after the IS Inter-Tournament where Laura defeat not once but twice by Ichika, She found her answer to becoming strong from Ichika Explanation in her deep consciousness(If is really Ichika said that or Chifuyu said that to her while imaging Ichika face), Anyway after that she save Ichika from Rin's Dragon Canon and kiss him, declaring to the whole class that Ichika will be her Husband(maybe that way she get two birds from one stone hehe^^)
Lastly No.5, "Cecilia Alcott" , She was the first heroine that argue with Ichika at the first day in IS Academy. She typical rich girl personality and very proud to tell her country.
For some reason i feel her less and less as a main heroine at the other episode
She become rank 5 in my list because the lack of reason fallen to Ichikan in the Anime, In the manga the reason why she fallen to him because just like her decease father have the same personality of Ichika. She sometime get alone with Ichika but not so often enough.
Well that all about the ranking & review of all 5 Heroine for the whole 8 episode.