Spoilers
He's just crazy not a rapist. Due to the the way the Miller siblings were raised Chase is the odd one in the family. And that's why Chase gets picked on by his family. Chase's dad was raised in a heavily traumatic environment and he tried to not pass that trauma to his kids and passed that to his kids.
Grayson never raped anyone. In fact, he understands very well what consent is. He's just a little crazy and has alexithymia. His story is very funny because his crazy way of seeing and reacting to the world makes things that are commonplace for us seem completely different from his point of view. But rest assured, he's not evil, just crazy and a liar hahaha

Novel readers, ive read from the comments that it looks liks greyson(?) have his own story... Well, i need a lil spoiler from his character because from what i can think off, he's a psychopathic rapist