I agree. Aina might see this as a challenge to make something better, but typically plagarism isn't seen as something positive/accepted.Can't speak on Japan, but I know that plagiarism definitely is not looked favourably upon at all by Western consumers. Especially with the internet and the notion of people stealing "ideas", its a very big thing. Its interesting to see how this manga will handle it because it really is a kinda dodgy thing for the MC to do.
Kind of hope the two will work together on something, or her drive will help him improve (and create his own story, with no inspiration from his magical microwave).