Hitori simply did not believe in the Crime Department at the Mage Ministry, that was the reason why he had not informed them about Kiku's death and Tengoku's attack.
To rely on the crime department was not an option. They would progress at the turtle's speed and would not even care enough to find the actual culprit or investigate what actually happened.
They will first spend half of the time investigating Hitori and other people he knew, then they would not make a move till his parents arrive. Amazing.
Hitori had kept the incident hidden from everyone, Kamiya did the same. So about Kiku's death, no one knew.
Hitori had tried to inform his parents about the incident through calls and emails but another day had passed and he had received no message from his parents.
Yesterday, Hitori tried to investigate a person known as Tengoku Kagaku. He did not have anything much on his plate but he got an overview of who this person actually was.