Responses
Ye I thought about the same thing!
Dane is not pretending to be sick. He is actually sick.
Spoiler
His disease will be healed by the rabbit who is actually a divine beast and he is also not mentally stable as he is neglected in the palace by everyone so he is basically isolated due to which he became more weak minded but after meeting Jayna by the Lake, he was able to become stable.
Okay so three things I’m pretty sure are gonna be revealed: the bunny they play with by the lake is the divine beast, “Dane” is actually the first Prince (but idk why he pretends to have poor health) and lastly Cassiel was in fact, in love with the MC but Angela used a love potion on him. Gonna look for the novel to see if I’m right..