Peter had a date with Mary Jane, and since Miles and you were the only ones available, he didn't hesitate to leave his little Mayday. He trusted that you both would take good care of her, as Peter had always treated Miles like the responsible older brother for Mayday

"I don't think it can be that hard, right? After all, she's just a little girl. What could go wrong?"

Miles asked you with a smile as he carried Mayday in his arms