Already posted my thoughts
here, but I'll paste the relevant portion, as it's perhaps more relevant here than it was there. No editing since my initial posting, so it amy come off as a little meandering and scatterbrained:
Hisao starts out as a nobody, a virtual non-entity. He has a few trivial character details, but nothing of any real commitment. In all honesty, Hisao starts out the story as Bella Swan. Right down to every single person of the opposite sex in the new school falling madly in love with him. Unlike Bella, his character develops.
At the beginning, Hisao does need the girls. That's what the manly picnic's all about. He has no convictions, no aim, nothing. This ties into the sexual politics running throughout the novel. With the possible exception of Hanako, it is always the girls who initiate, be it socialization or sex.
Emi sees that Hisao is depressed because his body refuses to let him do what he wants to do. She can sympathise, so she takes it on herself to be the white knight, rescuing poor depressed princess Hisao, giving his life structure and goals. In the bad end, Hisao becomes exactly like Emi, trying to carry all his troubles by himself. Everything falls apart, so he takes refuge in running as an escape from life. In the good end, Hisao accepts that you can rely on others, and ask for help (it's impossible to get the good end unless you seek or accept help). He realises that Emi gave him help long before he knew he needed help. He understands and accepts that he is able to stand on his own, but that life is better when you allow others to help.
Shizune sees Hisao's depression and decides that she wants to help him see how much there is for him to appreciate. She takes pride in her handiwork, in doing things for others. She is rather simplistic in assuming that everyone thinks much like her, so she enlists Hisao to push him, so he can see what he can do. She is quick to give up on him - if he has no fighting spirit, she sees him as a lost cause. Hisao makes a show of objecting to all the work and bullying, but he finds that his life has more meaning in doing things, along with enjoying Shizune and Misha's company. Becasue of Shizune's take-charge personality, Hisao finds himself coasting, allowing others, usually Shizune, to make all the decisions. In the bad end, Hisao refuses to take a stand, and takes the path of least resistance. He then makes his first actual choice in the relationship, choosing to shut Shizune out rather than admit that he made a mistake. In the good end, HIsao realises that he has to determine his own path. He takes charge of the situation, as he can see this is something that Shizune can't and won't handle. The story ends on an open note because the whole theme is Hisao's ability and desire to choose.
Lilly sees that Hisao is lost and aimless. He has no motivation, no aim, and Lilly can tell. Being of a motherly disposition, she takes Hisao under her wing, but realizes that she's not interested in a child, she's interested in a lover. Hisao, like a lost puppy, follows her wherever she goes. Lilly wants to stay with Hisao, but isn't certain that Hisao wants her to stay. In the bad end, Hisao never learns to stand on his own. He relies on Lilly for everything, but refuses to actually open up to her and trust her. Hisao's problems are Hisao's problems, and, by extension, Lilly's problems are Lilly's problems. Hisao doesn't trust that Lilly will stay with him if he asks, so he never asks. In the good end, Hisao has learned that Lilly wants to share her burdens with him, and is willing to share his burdens with her. He trusts her, and he also understands that she wants to be an equal in the relationship. He realises that Lilly need him to take a stand; he trusts that she will stay if he asks her. And he realizes that his inability to be an adult has led to his girlfriend/love leaving. So he decides to man up, do whatever it takes, and let Lilly know what he feels. His dramatic gesture crashes and burns, but it makes an impact.
Rin sees that Hisao is very much like her - directionless, adrift, with no sense of self. She doesn't trust herself or her words. She can't bring herself to say anything, so she uses gentle nudges. She makes excuses to spend time with him, couches her actions in ambiguous gestures, and tries to make sense of him, in the hopes that making sense of Hisao will help her to make sense of herself. Hisao finds himself coasting, just going with the flow, and they gradually find themselves fascinated with the enigma that is the other. They try to reach out tot he other, but whenever one of them is ready, the other isn't. In the bad end, Hisao gives up, refusing to try to understand Rin, or himself. In the neutral (also bad) end, Hisao sides with Nomiya - no one cares about understanding other people, it's all about the art. Hisao gives up on trying to understand Rin, because he feels it's a lost cause, and convinces Rin that understanding and being understood is a lost cause, so she decides to do all that she knows, because it's all she can know. In the good ending, Hisao realizes that understanding and being understood is a red herring. What both he and Rin are seeking is someone to whom they can connect. In finding that they can form a true connection, they decide that understanding and being understood wasn't all that important to begin with.
Hanako sees that Hisao is being nice to her, though she doesn't understand why. She allows him to get close, because she wants love and affection, but also because she sees that Hisao needs help, so she has something to offer to him. Every time Hisao does something for her, she seeks to return the favor. She relies on Hisao, but she wants to show him that she's strong, and that he can rely on her. In the bad end, Hisao has become dependent on protecting Hanako. He refuses to let her be strong, to see her as strong, because he has made protecting her his sole purpose. In the neutral end, Hisao doesn't stifle Hanako, but he refuses to see her strength, so Hanako remains in Hisao's eyes a delicate porcelain doll, appreciated and admired, but too fragile to be loved. In the good end, Hisao gives Hanako the space and opportunity to be strong, to let her use her own judgement, so much so that he stops even thinking about her fragility. He then learns that Hanako is actually very strong, so much so that she has become hard. They learn that they each unfairly misinterpreted the other's actions, but have accepted that they're both strong enough to repair the faults and rebuild their relationship on mutual trust and understanding.
In all the endings, good and bad, Hisao learns something important, which he will take with him later in life. The key difference is what it costs, of himself and of others.
