hannibal chau left eye

He just went into a public shelter during a kaiju attack and got injured. No drift. That's why he had his own private shelter made.

Exactly, Hannibal never drifted with a kaiju. Besides his face has knife scars around his eye.

Hannibal Chau never drifted with a Kaiju. Hannibal even told Dr.Geizler it was a really stupid thing to do because because the drift goes both ways allowing the Kaiju access to a person's thoughts/memories. That's why Dr. Geizler was so freaked out in the shelter, because Chau said the Kaiju (which are a hive mind collective) would probably try and hunt him down. The scar above Hannibal's eye was from his being in a crappy public shelter once, after that he made his own private shelter.