It is expected that Lee Yeongdo will write two more sequels, because of the quote in the series that mentions four birds. In the book there is a riddle about four bird brothers. One bird drank water, one drank poison, one drank blood and one drank tears. The riddle asks who of the four birds will die first. This riddle appears repeatedly throughout both "The Bird That Drinks Tears" and "The Bird That Drinks Blood", and is entwined with many of the themes that run through two series.