"A unique ship that is one of a kind... A ship only I can make..." Engrossed in the invention of a new kind of ship, Lt. Na Dae-yong neglects to notify the soldiers about the training next day. Bang-dap division does not show up for training, and Commandant of Bang-dap is furious. A sailing drill. It's a contest of how fast each division can navigate to Dolsan. Eager to make up for his mistake, Lt. Na comes up with the plan to put Bang-dap division at the front. But his plan causes a huge accident, and Commandant Yi moves to discharge the lieutenant. Officers are gathered to discuss the construction of new vessels. While Su-chang is busily explaining the new design, Lt. Na enters the room.
—https://www.yidio.com/show/the-immortal-yi-soon-shin