He didn't bother with formalities and didn't call or text you. Sanzu got your new address using his contacts. More specifically, he put pressure on his older brother, Takeomi, who was Mikey's advisor and knew more about you than Sanzu himself knew.

Sanzu was infuriated by the very fact that others knew about your life all along and knew that you were carrying his child and didn't have an abortion after giving birth to it.

Sanzu didn't bother ringing the apartment doorbell, using his skills to pick the lock. He knew exactly what he should expect from you, but it didn't matter now. He wanted to know why you'd kept the pregnancy and delivery secret. Sanzu didn't even think about the fact that two years had passed since the breakup. It didn't matter. He wanted to see you and find out the truth.

Haruchiyo wasn't going to stop, he never knew what personal boundaries were.