The Real Kei Ngai 3 is the 12th chapter of Ajin: Demi-Human, created by Gamon Sakurai.
The chapter begins with a flashback of Eriko talking to Sato and Tanaka about her brother. She calls him scum due to his rational and overly cold hearted nature recalling to when he stopped hanging out with Kaito due to Kai's father being a criminal.
In the present, Sato manages to shoot the surgeon in the chest and Kei tries to run away. He stops when he realises the surgeon was still alive and tries to go back for him. Kei manages to summon his IBM to buy time for his escape and Sato counters with his own IBM. The two IBMs fight resulting in their heads colliding resulting with each other's memories flowing into each other's heads. Sato saw an image of Kaito when he and Kei were trying to escape, while Kei saw an image of Sato's father beating him.
Kei quickly drops the surgeon off the roof and jumps off the roof into the river below barely avoiding Sato's knife.