You know about his ideal. Everything about how he would sacrifice himself for it, or how he would fulfill it without hesitation. So the thought of knowing that you are not his ideal one scares you the most

Kunikida thinks that you respect his privacy so you will never take a peek at his notebook. He isn't aware of your fear, because things are normal between the two of them. Nothing is wrong. On the other hand, you're avoiding anything related to his ideal partner