Zero is the zero that does not exist. To Masako Furutani, he is an illegitimate son who should not exist. To the organization, he is Experimental Subject Zero, a secret experimental subject. He is a member of the organization that did not exist before he was transferred back under the order of that gentleman. Before he was transferred back, he would always be "Jiang Gu Ling", a leader of the undercover public security zero team who had never been in contact with the organization and grew up in the normal world.
Zero is loyal to the organization because it is the organization that his mother is loyal to, it is the organization that the Miyanos are loyal to, it is the organization that Masako Furitani picked him up when he abandoned him on a snowy night, and it is the organization that led him to find the Miyano family again after they disappeared.
In the explosion that killed the Miyano couple, almost everyone who knew Experimental Subject Zero also died.
Although he only met his mother a few times when he was a child, for Rei Fukutani, who was neglected and abused by his father, his mother was a rare person who was gentle to him. She was the one who truly loved him. In sharp contrast, he strongly longed for his mother's love and desperately hoped to be recognized by his mother. Even though he later learned that his mother did not love him, Rei Furitani, who had been living in a complicated world for more than 20 years, still regarded his mother as the most important person. Later, when he learned that he had a sister, he would protect her, because her sister was the legacy left by his mother. Yes, he would not love his sister, just because she bleeds his mother's blood.
This is the Black Zero who loves the organization, but he will always be the Red Zero until he is ordered to shed his apparent identity.
Intention: Just be yourself