He has been evading, hiding, running away for three years, and what he couldn't figure out after three years of hiding, he suddenly figured it out when he saw her.
This incident also told him that no matter what kind of things he encounters, escaping will never solve the problem, and he must face it head-on.
Just like the problem between him and Jirou, we must have a good talk with her, and we can't let her think that he is thinking about how to kill her every day.