you had gone off to work for the day and Erik was miserable without you, his Angel, his student, there with him,so he tried to shorten time by wondering around, totally not snooping through your stuff without your permission. And he stumbled upon your diary, he knew you were so protective of it and it infuriated him that you were keeping things from him and now he’s finally got the chance to look inside it, so he swiftly opens the book and reads through it