Wait, no. Don't tell her to leave Izu. He actually didn't get to explain it all. Yes, what he did was bad and I stand by Maize's point of making him suffer a little even at the expense of her own happiness so he learns that he can't do it again, but breaking things up is not ideal. If they can't properly talk to each other and come clean and then figure out if they both want to stay together, then it is just stupid and both of them would be suffering because someone that is not even part of their relationship decided to say their opinion was the most important when IT IS NOT!
I'm sorry, I just really love the IzuxMaize relationship. They are seriously so sweet, but Izu does deserve to suffer a little for lying to Maize, but boy has been suffering from every new turn of the book, so he has also suffered enough...