There are actually quite a few former capitals of Japan whose English names have 5 letters: https://en.wikipedia.org/wiki/Capital_of_Japan. Other than the currently accepted answer, the most well-known are probably Asuka, Osaka, and Heian.
Though I will readily admit that anyone who has heard of these (especially Heian) has probably also heard of the currently accepted answer ;)
Shouldn’t the “France in WW2 be changed to “Vichy France?” The capitals both have five letters. Although Vichy France is kind of a giveaway, so maybe something else?
Missing Vichy was one of the more frustrating experiences on this site. I am a major WW2 buff. I use the term 'Vichy France' all the time. I do not know why it slipped my mind in this instance. It's like forgetting how to ride a bike. Maybe I should get better sleep or something.
Though I will readily admit that anyone who has heard of these (especially Heian) has probably also heard of the currently accepted answer ;)