User blog comment:Koishi-Komeiji/Miyu Edelfelt/@comment-4802891-20180902120439/@comment-24965192-20180902124535

I think she still uses beams like Illya does as a Caster. Somewhere between a mix of a Lancer and Caster move set is what I would describe Miyu. About being able to install other class cards, I believe Phantasmal Summoning is disabled when you're a Servant? Illya can never use her class cards as a Caster due to this limitation. I guess some lore part which I would have to explain later has landed her in the Lancer class.