flat what wrote:Ahem. It's indeed stupid to assume that girls easily break their close friendships for a relationship, but it's also not like everything will go on like always.
An interesting point. I only really see what happened to you happening when Hisao ends up with either Rin or Emi. Those two are the least close of the other friend pairs. Their relationship isn't really to help the other function, not critically, though Emi enjoys helping Rin in her day to day life. I can see Hisao changing the dynamic of their friendship easily, though it probably wouldn't affect the other too much. They can get along fine on their own.
With Lilly and Hanako, I feel it depends on who Hisao gets with. If he gets with Lilly, Hanako would still cling to her like her mother. Lilly is still Hanako's main source of emotional support, and her only friend. Hisao will help Lilly help Hanako, and the three would remain close for a long time. He would become the 'father' of this dynamic. If Hanako gets neglected to the extent that you were, she'd have a breakdown. It gets interesting when Hisao chooses Hanako. She may be reluctant at first, but she may be weaned off of Lilly, and use Hisao more as her main emotional support. It all depends on how the story goes, of course. Lilly might see less and less of the two lovers as they progress in their relationship, but she is mature enough to handle this.
On to ShizuMisha. As I have said before, Misha is too close to Shizune to be separated easily. She serves an important functional role in Shizune's life, as her ears and mouth. Hisao is going to have to learn sign language to be with Misha, but he won't be proficient enough to functionally replace Misha for a long time. She may even be Hisao's teacher, if the hints in act 1 are to be believed. But really, for years Misha has been one of only a few to share in Shizune's world. She's probably the best friend she's ever had, her closest confidant. And I don't think she'd forsake her, even for Hisao. I'm talking potential life long friendship here.
You can actually see these in the Act 1 endings. On both Emi's and Rin's paths, the other girl in the pair is missing, leaving Hisao alone with his chosen girl. On Lilly's path, he spends the festival working with Lilly to help Hanako, and the two share a nice moment at the end. On Hanako's path, Hisao sees Lilly about Hanako, and he spends the rest of the day alone with her. During Shizune's end, Hisao watches the fireworks with Shizune, but he spent most of the festival with both Shizune and Misha.
It's a good thing Shizune is deaf, she is the only one who can stand (not) hearing "Wahaha~!" over and over.