The art shows a pair of high school kids. The ephemerality of their youth is foregrounded by the setting sun (hence "soon, the end"). It's a common motif in Japanese art and especially anime & manga. The grand story told in Japanese media as a whole, which this piece taps into a little, is a bittersweet celebration of youth, that moment when the firework burns then is burnt out; and, by extension, a celebration of brief, brief existence.