Not knowing at the time about its connection with the anime "Maison Ikkoku"（めぞん一刻）, I used to listen to Yuki Saito's （斉藤由貴）5th single, "Kanashimi yo Konnichiwa" (Hello, Sadness) pretty often on one of those compilation tapes of aidoru songs that I got from Chinatown. To me, it was the quintessential aidoru song with the intro synths and Saito's slightly off-tune and quivery vocals.
The lyrics by Yukinojo Mori （森雪之丞）related how even the saddest memories would still be welcomed and embraced as old friends by the singer, while Koji Tamaki's （玉置浩二）music represented a certain hope and defiance and perhaps even a defense of those melancholy feelings. I guess there is something about the Japanese psyche that just loves to protect even those emotions instead of driving the blues away as they would be treated here.
I think with those huge puppy-dog eyes and soft vocals, Saito was probably the best aidoru to relate the lyrics. "Kanashimi yo Konnichiwa" peaked at No. 3 when it was released in March 1986 and later became the 19th-ranked song for the year. She also got invited onto the Kohaku Utagassen in December for the very first time and was instantly made the Captain of the Red (Women's) Team! I remember my parents were far from impressed with Saito's leadership since she seemed to be giggling throughout the broadcast. I was rather surprised myself at the promotion but I figured that Saito was probably bleeding off some nervousness through the laughter.
The song was also a track on her 3rd album, "Chime"（チャイム）, from October 1986 which got as high as No. 2. And along with its usage as the very first theme song for "Maison Ikkoku", "Kanashimi yo Konnichiwa" was also the commercial tie-up song for some Shiseido cosmetic product.
The above is a video of Saito and Tamaki performing a ballad version of the song.