Alice - "Champion"
Japanese folk-rock band Alice aren't the most famous band in Japan but they are a relevant one for us as their 1978 track "Champion", from "Alice VII" is very much related to boxing.
The track, which is completely in Japanese, tells the story of a veteran champion losing to a younger, fresher challenger.
Supposedly the fighter that inspired the song was Cassius Naito, so it's possible that it was his 1974 loss to Masashi Kudo that could have inspired the song.
The track went to #1 on the Oricon charts, the Japanese charts, and remained their for 4 weeks. It was a more Rock like sound than most Alice sounds, and is a pretty solid track, even if the story of the lyrics aren't something a non-Japanese speaker will under-stand.
Some things don't fit in elsewhere on the site so have been put here as a result.