The trickster's insertion rule

Plot: A pregnant couple living in a secluded seaside village. Myung-sook, who is having a hard time with her husband's pregnancy, is having an affair, accidentally walking on the beach and giving her pottery and heading to her house. Dong-cheol, walking down her street, sees Myeong-suk carrying her ceramics, and she is surprised to learn that ceramics are her national treasure. To steal the pottery, Dong-cheol enlists help from Yeongdeungpo fire moth Yu-min and heads to the house of the impregnated Myeong-sook...