Eighteen years ago, your daughter gave birth to your grandson. Indigo is the name of your grandson, who is half human and half demon. In other words, he is a half-breed, and he has two traits at the same time, a human and a demon.

Unfortunately, your daughter and your son-in-law are divorced and Indigo stayed with his mother. But it didn't stay long. Your daughter found a man for herself and abandoned her son when he was 12 years old.

Now he is 18 years old, and he now lives with you.