Responses
The reason for that is because in the novel it explains that chika while as a sex slave he had masters that would force him to act younger then what he was. And when he didn't I think they removed his voice from him. But still made him move and do gestures of a younger person. Also those two at first thought he was a child still because how small, frail and young looking he looks, accompanying the way he carries himself (because of the previous masters) so even after being told his age and also mental age those two were actually quite shocked to know he was a adult.
chika’s age is one thing but even more than that why are they treating him like he’s a literal baby? carrying him around everywhere ALL the time lol i swear there’s not a single chapter where chika isn’t being carried