use past/present tense when talk about general facts in an imaginative...

Well, I need to write an imaginative story. It is about my experience with a ghost in Tokyo two years ago. Of course it is not real ...

"He was a very kind ghost, so we became friends. I told him that Tokyo was/is a big city in Japan."

Should I use "is" or "was"?? "Tokyo is a big city" is a general fact. (well, you may not agree but let's not talk about this) So I guess we should use present tense in a normal reported speech. However, as it is a story, it is not normal. Past or present?

Any opinion will be apprepriated.