Good day, everyone.
I've started reading a Japanese version of Little Red Riding Hood I found in
how-to-learn-any-language.com:
www.aozora.gr.jp/cards/001091/files/42311_15546.html
The first sentence is this:
むかし、むかし、あるところに、ちいちゃいかわいい女の子がありました。
I noticed that it is using 'arimashita', but the subject is 'onna no ko' right? Why 'arimashita' is used, and not 'imashita'?
Thank you very much for reading this question.

I will appreciate your answers. Thanks so much.