She was trained to act like a 5 year old? It doesn’t matter how an idol is supposed to act with her fans, that’s not how a high school girl would act when interacting with real people who are trying to help her.
Not only that, but everyone around her treats her like she’s five. Nao talks with Misa’s friends about Yusa having powers and being in danger right in front of her, as if she’s not even there. And she acts completely oblivious!
Seriously, the actual Key five-year-old acts and gets treated with more maturity than Yusa does. We can only hope that this will change with the episodes to come.