Ouch, that must have been an annoying experience. I haven't beaten the game yet, but i'm on the 7th day and i've already picked my route. The game is just too damn awesome :0
As for Io, I don't think she's similar to Yuzu; Aside from the prominent boobs, they're completely different in terms of personality. I also like like how she's not totally into the MC throughout the game, like Yuzu was (I didn't mind it too much, but sometimes it got annoying in the first game) and stat wise, while they're both mages Io's secondary stat is Strength, giving her a unique (but odd) stat spread. You'll like her a lot more later in the story trust me.
Daichi's pretty damn awesome too. He's also pretty damn different from Atsuro (I think the only similarities lie in their smiles / eyes) Though he's comic relief most of the time, he gets his moments, and eventually becomes a big damn hero.