Seems obvious that Shinozuka is Pomeko, but now it's confirmed. Interestingly, she was also betrayed by his betrayer's new bestie. Our boy needs an ally in this crapsack life, and I feel that she needs one herself. I'd be surprised if they don't become that friend to each other (and maybe lover later).
I do wonder why these bad girls are suddenly trying to patch things up with him in high school. Did they suddenly realize what they did was wrong and felt guilty, yet for some reason stop short of actually acknowledging their wrongs to say sorry and instead either downplay the pain and harm done (Shizuka) or outright pretend it was all his fault (Haruka)? Or was it simply just because he's good looking now despite his ruined reputation?
I don't know if his ex-childhood friend was also as two-faced as the other girls, but that level of blissful ignorance on her face is just as insulting as if she deliberately ignored his suffering in the past.
On a side note I'd like to call this the anti-harem: the story seems full of girls who are enemies instead of love interests and who the audience is expected to root against. I don't see this kind of thing often, so it actually feels kinda refreshing to me.