Daigo was the lord of Ishikawa domain which was ravaged by floods and starvation due to poor harvest. He made a deal with a group of 48 devils (12 in 2019 version) in order to save his domain and to aggrandise his power. He promises each devil a body part from his unborn child in exchange for the power to take over the land.
Towards the end of episode 24, while dying from the side effects of having made a pact with the demons, he is seen regretting having sold his son to the demons and realises that it was the will of Hyakkimaru to live on that the demons craved for and that perhaps, if he had succeeded his reign, the prosperity that he desired would have been fulfilled.
