It's a pretty stupid concept to have those "tsugai" - fully conscious and capable of logical deduction beings - act as robots that can only "do as commanded" by a "master". Especially more stupid when they're capable of realizing a command such as "do as you wish", meaning they also have their free will. This happens a lot in manga, it's stupid as fuck and a huge check-off for me.
No matter how hard I try, I couldn't switch off my brain to follow these braindead stories.