Arguably the most famous Off Course (オフコース）song of all, I remember hearing this and wondering if this had been the tune the band broke up on. It just sounded so sad, wistful, proud and celebratory at the same time. It's probably a song that companies use at staff farewell parties for particularly popular employees.
Before I figured out the lyrics, I was just drawn by Kazumasa Oda's （小田和正）voice, resigned and wistful at the beginning and the end but during the chorus, filled with pride and anthemic. Although the lyrics spoke of a man looking back wistfully at a past romance, the music seemed to fit any sort of coda for any sort of experience. It's been written on the J-Wiki writeup for "Sayonara" that after this song came out, the band went from a folk-rock sound to a New Music/AOR beat. On reading that, I'm now wondering if that electric guitar riff in the middle was a goodbye of sorts.
Also on the J-Wiki writeup, Oda said: "I wrote (Sayonara), strongly intending to sell more than we ever had before", and sure enough the song became Off Course's first million-seller. It also peaked at No. 2 on the Oricon weeklies and became the 9th-ranked song of 1980. The single was released in December 1979 but was later included on the band's 2nd Best album, "Off Course Selection 1978-1981"released in September 1981 which peaked at No. 1.
On YouTube, I've read that a lot of people loved the concert version even more than the recorded one, so I've included it here. I'm pretty sure that there wasn't a dry eye in the house when Oda sang this one.