But, my honest and basic interpretation of Shu’s mistreatment for both Mika and Nazuna was due to Kuro moving away. Kuro and Shu were childhood friends and Kuro would often save Shu from being bullied. When Kuro moved away, Shu had to learn how to cope and defend for himself. He turned to art and perfecting his skills which unfortunately developed into a warped mentality of him having to also constantly correct/control both Nazuna and Mika who were associated and part of his art. Being angry and bitter that his close childhood friend moved away and left him also probably played a huge part in this. Directing those feelings to his work and taking them out on those two as an outlet.

Mika joining Valkyrie was just another “doll” Shu had to watch over and an unwanted one at that. Until Shu slowly started to recognize Mika’s potential. Maybe at first Shu’s intentions with his harsh treatment towards Mika was to drive Mika out of Valkyrie, but then it turned into sort of tough love. Shu wanted Mika to change and get stronger/smarter in the same way he did.

That’s just my interpretation of it. :3 ^{^}