For a harem manga, IHP really surprised me. There's a lot of depth I wasn't expecting, and the story and characters are really well composed. The ending sure hit me like a ton of bricks though. Everything builds up over the first 16 volumes, and then it just feels like everything comes crashing down starting with volume 17. Not that "crashing down" implies anything bad, but all the emotion and excitement built up over all those pages really hits hard when you realize it's all coming to an end, and there's nothing to do about it.
Without spoiling too much, I would like to get my $0.02 in about the ending. As a harem, the plot focuses around 4 girls who fall in love with the central character, Manaka. Generic and overused as this may be, all the characters are really well developed, and I ended up being able to sympathize with all of the girls' positions. I think in this manner, it's possible the author wrote herself into a corner. But her handling of the ending was pretty good -- in fact, I'm not sure it could be handled any better, given the circumstances in the story. But my problem with the ending has nothing to do with what girl he ends up with. It's that it's actually "the end". In the sense that, after high school, people end up going their separate ways, and life really just changes fundamentally. It's a tough turning point to deal with in real life, so it's tough reading about it with well-developed characters that you can actually feel attached to, provided you can get into the story.
Speaking of getting into the story, for a title with such a simple, childish initial premise, IHP actually delivers quite a lot of depth. It's a "coming of age" type of story, so there's a lot of exploration of developing emotions, and the meaning of love, and friendship. It's tough sorting out conflicting feelings when you're experiencing them for the first time; What is love? What makes it different than having a great friendship? Where is the line dividing the two? How do you deal with a one-sided romance, when your feelings are strong enough to make you willing to hold out for the chance no matter the odds? These questions, and more, are explored, and except for the ending (hey, the author had to end it sometime), they're mostly left for the reader to think about -- things are presented, characters react differently depending on their personality, and then you're left to think about it all.
I also enjoyed -- as I realized about 6 or 8 volumes in -- that the characters change over time. Manaka's a naive, bumbling, indecisive idiot at the start, but he actually grows and learns from his mistakes (even if he doesn't end up always acting on what he learns, he still realizes he's making a mistake). In the same manner, each of the characters deals with their own problems and feelings, and there is some growth, which I really appreciated. Otherwise this title would have been so repetitive and boring by a few volumes in, I'd certainly have dropped it.
The one overarching message I got from IHP, though, is to not let yourself be too indecisive. It's important to know what you want, and make decisions based on that - not leave things hanging and unanswered. Manaka has a real problem with his indecisiveness, and it ends up hurting every single one of the characters in this story - tremendously. In the end, he does learn to deal with it, but it is difficult watching him continually leave things without making any choice. The one refreshing thing about Manaka's indecisiveness is that he never allows himself to actually take advantage of any of the girls in a way that they may later regret (or that may hurt the others). While that's also an extremely frustrating aspect of Manaka's behavior, it's one that I respect, and am grateful the author went that direction with him.
I hate to sound like I'm gushing over what, on the surface, seems like a cheap ecchi title whose sole purpose in existing is to satisfy the carnal desires of pubescent teen-age boys, but Ichigo 100% was seriously one helluva ride, and although I found myself frustrated at a lot of points, it was, in the end, quite a fun ride indeed. Get past the never-gonna-happen dramatic buildups with no climax (grrr, Manaka), and it's likely you'll thoroughly enjoy this. Don't, and you probably won't make it past the first couple of volumes.