Yet another song by the title of "Sotsugyo" (Graduation), but unlike the aidoru tunes by Yuki Saito and Momoko Kikuchi（斉藤由貴・菊池桃子） or the protest ballad by Yutaka Ozaki（尾崎豊）, Misato Watanabe's（渡辺美里） 19th single from April 1991 is about the closest to sounding like a good old-fashioned graduation song that would be played at the annual school ceremony.
I remember when Watanabe performed this on an episode of "Music Station" or some other show. She sang this under a huge mockup of a brilliantly-lit blossoming cherry tree on an otherwise dark stage. It was just about Kohaku-worthy in the setup. The lyrics by the singer herself reveals the uncertainty of leaving school and friends, including one in particular, and paired with Tetsuya Komuro's（小室哲哉） near-elegiac melody, I wouldn't be surprised at one point if the song had actually been used at some of the schools. Strangely enough, it was used as a campaign song for a life insurance commercial, but I guess one is never too young to start paying premiums.
The single also belonged on Watanabe's 7th album, "Lucky" which came out in July 1991. It not only hit No. 1 on the album charts but it ended up as the 9th-ranked album of the year.