"Unbalance" was Naoko Kawai's（河合奈保子） 14th single from September 1983. I first heard it at the Kohaku Utagassen from that year, and noticed it had more of a disco beat when compared to her 1981 Kohaku entry "Smile For Me". But then again, when I go over the first several years of Kawai's career, I notice that she dabbled into a few other genres such as Mariya Takeuchi's（竹内まりや） bobby-soxer ballad style and the AOR from her 1985 album, "9 1/2".
As for the disco beat, well, according to J-Wiki, composer Kyohei Tsutsumi（筒美京平）was probably inspired from Donna Summer's "She Works Hard For The Money" which came out the same year. Masao Urino（売野雅勇） was behind the lyrics. It peaked at No. 4 on the Oricon weeklies and ended the year as the 64th-ranked song. It also appeared as a track on Kawai's 7th album from October 1983 titled "Half-Shadow"（ハーフ・シャドゥ）which went as high as No. 2.
I don't know...I always look at that title and just end up wondering about the balance of power in The Security Council at the United Nations for some reason.