Sasebo station is the terminus of JR Sasebo line. Then, it is the main station of Sasebo city which is second largest city in Nagasaki prefecture.
Not like Nagasaki which was the important port and trading post for Dutch merchants during Edo period, Sasebo was built after the end of Tokugawa shogunate.
Sasebo was elected as the major naval port for newly established Japanese Imperial Navy in 1889.
Sasebo has a very good conditions for operating the naval port - location(close to China and Korea) and natural harbor(deep water).
After the disband of Imperial navy after WWII, Sasebo became the naval port for US Navy and Japanese self defense force.
Therefore a lot of foreigners are using Sasebo station, mostly US military personnel.
You can reach Sasebo from Fukuoka's main station, Hakata station by limited express Midori or rapid train Seaside liner from Nagasaki.