Arc Fatigue: The second half of the manga suffered from this, especially after the introduction of Kozue, who was nothing but a blatant (if sympathetic) Romantic False Lead, and is often referred as a "filler character". And considering the ending, many feel why the story was prolonged for so long since Junpei made amends and started to date Tsukasa again around the middle of the history and this never changed until the end.
Ass Pull: In the 2nd half the story it's revealed Tsukasa had feelings for Junpei before the beginning of story. Some fans considered it a blatant attempt to turn Tsukasa into the first girl. Also, this created a small plot hole in the story since Tsukasa had other boyfriends in the past and never tried to get closer to Junpei despite having feelings for him during that time.
Awesome Art: Manga only. Mizuki Kawashita's art style, which finds a pretty good balance between realism and shonen-like stylization, is one of its main selling points.
Junpei, in general, has it better than most other harem protagonists, mostly because his dream of being a film director gives him much more personality, drive and agency than the usual self-insert protagonists that usually star this kind of stories (even if he still falls into some of their usual traits). However, he still gets some flak for how long it takes for him for making up his mind about his feelings, to the point he made Tsukasa, Aya, Satsuki and Kozue to suffer at some point due his indecision. Also,the fact that he suggests to break up with Tsukasa the second time to focus on his dream of becoming a film director is a sore point for some. Somewhat alleviated by the fact that it was meant to be a temporary break-up so Tsukasa could also go to Europe with a more clear conscience, and that they agree to try dating again when the time comes.
Also Aya. Although she was the favorite main girl for a big chunk of the fanbase, mostly because they argue she was the one most compatible with Junpei in both personality and life goals, there are also people who dislike her for how passive she was for the vast majority of the story. This is in contrast to Tsukasa, Satsuki or even Kozue, who were much more romantically active than her. Some go as far as to say that she has no one but herself to blame for losing Junpei, since she had plenty of opportunities to win him over, and she let pass every single one of them until it was far too late.
Broken Base: The ending in general, albeit it depends heavily of which girl you were rooting for. Supporters like it specially because Manaka doesn't choose the girl who seemed, at least at first, like the most likely choice, and conceded that Tsukasa "earned" to be the one. But others argue that, again, Aya's personality and life goals aligned with Junpei's much better. See Ending Aversion below for more details.
Ending Aversion: The ending was very criticized by various reasons and especially by Aya and Satsuki fans. First, the girl who Junpei chose, Tsukasa Nishino, is a major Base-Breaking Character. And the reasons which led Junpei to chose her only added more insult to the injury because it's unclear if Junpei is dating Tsukasa for love or just for making amends for being a bad boyfriend. Aya Toujou had a lot of trouble to overcome her feelings after being dumped and looks like she still loves him considering her facial expression in the final chapter. Both Aya and Satsuki stayed single, meaning their endings were bittersweet at the best. And despite being the victorious girl, Tsukasa only appears in the last pages of final chapter. Also, there are people who think Junpei didn't deserve to be with Tsukasa or the other girls for what he did.
Family-Unfriendly Aesop: In the last chapters the story toys with the idea of love being an obstacle in the path for your dreams. This is more evident when Junpei feels both Aya and Tsukasa will have a brilliant future ahead of them while he is in the rock bottom and doesn't know what to do. His plan? Dump Tsukasa, forget Aya, stay single and pursue his dream of being a Director. Although he aborted this plan in the last minute, he and Tsukasa had an agreement about pursuing their dreams and resume their relationship after finishing their studies, which only reinforced the point of "love being an obstacle".
Fan-Preferred Couple: Many people wish that Junpei picked either Aya or Satsuki over the actual winner, Tsukasa.
Ship-to-Ship Combat: Pretty much inevitable in a harem series. The main three girls, Aya, Tsukasa and Satsuki, all have their respective share of followers.
The Scrappy: Chiname, mostly for being a manipulative gold digger. Many fans feel she was unnecessary in the story, stealing the spotlight from the heroines.
Ookusa. He quickly disappeared after the first year, only making small cameos and he was almost absent in the second half of the story. He could have been an interesting Foil to Junpei considering their opposite places in life, and while he was still relevant he helped the boy with his relationships.
Kozue. She debuted too late in the story when [[spoiler:Junpei was between Aya and Tsukasa only, with Satsuki almost out of contention. Although people think her crush on Junpei was actually fairly well written, and she had some focus in a few chapters (being more active than Aya herself despite the fact that she is an even bigger Shrinking Violet than her), she quickly becomes just an extra character, thus feeling like a pointless Romantic False Lead. The same could be said about her friends.
The Woobie: Satsuki. If any of the girls could be labeled as a tragic figure, it would be her; despite her total devotion and physical advances, Manaka constantly rejects her. In the her last chance she ends the scene in tears. Poor girl.
The sequel, East Side Story
WARNING: Uncovered Spoilers from the original series below
Awesome Art: Kawashita's style improved a lot in the 12 years between the series, being more beautiful than ever before.
The length of this new story, which reaches only 4 chapters. Some fans feel it was a wasted opportunity considering how Kawashita's art improved over the years and how much room for more content this new story had. Others are pretty happy this ended quickly, especially Tsukasa Nishino's fans which were worried about Aya getting Junpei, retooling the ending.
Replacement Scrappy: Nakama. Although a few fans call for patience and see where the series goes before judging him, most of them are really not happy with the fact that he is basically a doppleganger of Junpei, both in looks and personality. A lot of people wonder how this setup can possibly have a satisfying ending, especially if he and Aya do in fact get together. Even Mizusu lampshades that, maybe doing so could mean that Aya just can't get over Junpei and move on.
The Woobie: Aya. She still hearthbroken for being dumped this is affecting her job as writer.