The author states that Ayumu did not steal Yuu's phone, she merely had a replica of it made for some wholesome play with blocks, such as mounting the replica with her own phone in her spare time.
nothing wrong with that whatsoever, what sells, sells
It's wrong, this is bad thing to do, look, I don't care if it sells, there have many ways to "sells", like entertain your viewers, being funny, not like faking a relationship while accidentally making a connection and ends up heartbreak those who you make connections with, that's just evil.