"Flasher" contacted another well-guarded tanker convoy on the morning of 21 December 1944, and she began a long chase, getting into position to attack from the unguarded shoreward side. In rapid succession, "Flasher" attacked and sank three of the tankers (Omurosan Maru 9,204 tons, Otowasan Maru 9,204 tons, and Arita Maru 10,238 tons), receiving no counter-attack since the enemy apparently believed he had stumbled into a minefield. One of these tankers was the largest "Flasher" sank during the war. The other two tankers had displacements similar to each other, were tied for third largest.