This article is not long, and it can't even be considered a novella. It is the first part of the series [Make a World for You]. I may write about Naruto or other anime in the future.
This shouldn't be considered Itachi's bg story, because from the beginning to the end, the heroine is the only one who has unrequited love.
It seems that the heroine doesn't like Itachi that much.
Generally speaking, it should be unrequited love caused by misunderstanding.
So be it.