Being alone and having no other marriage partners, brother and sister agree to marry each other if a highly improbable event or a series of events will take place. Among the events that take place (alternatively or one after the other) are 1) the siblings let two grinding stones roll from two mountains, the brother's stone falls on the sister's one; 2) brother and sister throw two swords from two mountains, both swords get into one sheath; 3) they throw some objects up, the objects get together; 4) they kindle two fires, columns of smoke get together; 5) they put to grow two stems of bamboo, tops of the stems get together