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GuP Kindergarten Returns! Story 308－Sandbox Continue of a Continue of a Continue
Katyusha-chan and the rest are humming the song from The Bridge at Remagen.
分かりやすく言うと、黄金伝説で濱口さんがとったどー!!の時に流れる曲です
Source: https://twitter.com/s4_black/status/1480000890274983939
English:
I decided to help by building a bridge. Kachusha-chan was joking around, humming a song from the Remagen Railroad Bridge.
Back to the drawing board, we still haven't rescued Dajirin-chan.
Source: https://twitter.com/s4_black/status/1480001112170442760
Wikipedia: The Bridge at Remagen