Noah didn't know that Kai knew he had gone into hibernation mode two years ago. He checked the details of Kai's and FERN's contracts. They clearly said that what happened to Noah during those two years was confidential and only a few people knew about it. Kai wasn't allowed to know what had happened to Noah two years ago. That was the rule.
He didn't want to let people know about his struggles back then. According to the laws regarding active Espers, what Noah did was basically counted as neglecting his duties, and EGUO had the right to punish Espers who violated these regulations.
FERN did their best to hide this by telling EGUO that Noah was having a hard time with guiding after Jayden's death.
Noah was totally blindsided when he heard Kai's thoughts. He turned off his psychic abilities as quickly as he could and quickly went into his own room. His body was shaking.
