Why does this map most likely shows the location of the city of kokura

Kokura was the original target for an atomic bomb that someone was planning to aim. But, the plane was obscured by clouds and the bomb hit the second target, Nagashiki. People in Japan refer to this as the "luck of Kokura."   Kokura is also in Kitakyushu, which is the second most populated city on the northern island Kyushu. These could both be reasons as to why kokure would most likely be shown on a map. If you are reffereing to a specific map, these reasons may apply as well, but if not, I tried my best.

to demonstrate that Kokura was the original target city for the second bomb

Explanation: