Was it just my imagination or that Kaede a bit odd? He lacks something in him…He's similar to Bran's change of personality but more alive and can perceive everything the same as a human.
Lina is the kind of person that can sense the oddity of the people she met since she was young. Made her aloof and childhood a bit lonely. That was when she met Sally which changes her completely.
While deliberating, Lina went outside to see if their family's elite bodyguards are really asleep. To her exasperation, Kaede was right! This really proves he is not a normal person. No wonder he is investigating a weird case like this.
One minute had passed, and the bodyguards jolted and shook their heads. Lina can only sigh and decided not to put her nose where it didn't belong.
No matter what happens, Kaede is not part of her investigation. This is a person ever her family cannot take on.