𝐜𝐫𝐞𝐬𝐭 𝐛𝐞𝐚𝐬𝐭.
Unlike in his original canon , Kamui cannot fully turn into a dragon in his Fire Emblem : Three Houses verse. The experiments he went under stripped the pigment from his hair (it was originally black) , and with a second crest woven into his blood , they had attempted to enhance his strength. More specifically , they wanted to further draw out the power of the dragon within him. It worked! However , it goes out of his control. As his teeth grow sharp , his gums grow sore , as his antlers sprout , he bears migraines , has his wings unfold , his back curls over , agony consuming him , as his tail grows he loses balance with the weight of it , forced to succumb being on all fours. His claws are one of the only things that do not cause him direct harm , but he does have to file his nails back down when his fingers return to their normal length.
All conscious awareness of himself disappears.
His whole body aches as a result for long thereafter. The only way to control this side of him is to let it consume him , and for him to reign control over himself again. But he’s scared , and others are scared of him. It mostly triggers itself , as opposed to being something he summons at will. Mostly through immense emotion , such as fear or anger , does it emerge from him.
There are often times he tries to practice ruling over it , because he fears the day it’ll rule over him and he’ll inevitably bring harm to others. So he wanders far away , far away , to train and combat with his self restraint. He’ll come back to the monastery , sore , sunken , bruised and cut up. Sometimes the only way to calm himself back down is to wear it out of him , in the nicest of terms. He doesn’t always win.
As for his normal , physical appearance , he unfortunately does withhold rather abnormal attributes. His eyes are red , pupils like slits , long ridged ears , his canines are the least noticeable as they are relatively the same as a humans , just slightly bigger. His fingernails are for the most part filed down to a normal length.
In short , he does not have complete control over himself , esp pre-timeskip. As time wanders to post-time skip, he has better manipulation over his powers and uses them to his advantage , however , sometimes the aches still follow.
“ What about his clothes? What happens to those once he transforms? ”
He does wear specific magic enhanced elastic that molds with his body! It was a gift .. from his dear siblings. So he won’t be naked!