KANA-BOON open with いっせーのーせ (roughly "ready, set, go!"), the call kids shout to start a race or a dare together, and then a "go line" they step over. Straight after comes the blunt admission 僕らは何も何もまだ知らぬ ("we still don't know anything, nothing at all"). That old-fashioned 知らぬ instead of everyday 知らない gives it a slightly solemn ring. Cross the line, look back, and もうない ("it's already gone"). That is childhood in two lines, and the rest of the song keeps looking over its shoulder at it.
The title word is the key image: 誰も彼もシルエット ("everyone has become a silhouette"). The people from those summers are now just outlines, faces you can't fill in anymore, because time keeps 奪ってく ("taking them away"). The singer even admits he 忘れたフリをした ("pretended to forget") what mattered to him. Then the song turns. One person stays: 消えぬ消えぬシルエット ("a silhouette that won't fade"), the one who taught him that some things never change. His answer is to carry what he cares about into adulthood and hold on, so that one day he can なにもかもを笑える ("laugh about all of it"). The falling leaves drifting ひらりとひらりと (a sound word for something fluttering lightly down) are the mood in one picture: he wants to live like that, with no worry and no rush. It is a very sweet ending for a song that started out so sure everything gets lost.
KANA-BOON are a rock band from Sakai, in Osaka, Japan. They started out in a high school light music club and became a proper band in 2008. Fronted by singer and guitarist Maguro Taniguchi, they signed with Ki/oon Music in 2013 and put out their first major-label album, Doppel, that October.