Konchi
Konchi shows up a lot in the '70s flashbacks as part of Kenji's childhood crew, though he never makes it to adulthood in the story. He was in the band with them back then and genuinely close to Kenji and the others, but that's basically all we get to see of him—because he moved away during his final year of primary school to Hokkaido. That's why he's barely around.
Things pick up again in 2000 when Kenji sends him a letter asking for help. They don't actually end up meeting though, and it seems like Konchi's got some regrets about it by the time we check in during year 3 of Ami's story. That's when he reappears: he's broadcasting one of Kenji's songs on loop from his radio station up in Hokkaido.
Content compiled by AnimeList.moe from publicly available sources.
