Ichiro Heian! - Vol. 1 Ch. 5 - Reclining Dragon Crossing Over a Great River

[MangaDex]

 

[LemonLies]

Just in case people care, the kanji for Tokyo are "東京" which means "eastern capital". Meanwhile Kyoto is "京都" or "capital metropolis". So she's made the natural assumption that these places are right next to each other, and bordered by a "Saikyo" (西京) or "western capital".
On a related note, Beijing is "北京" or "northern capital".