Inoya Daisuke was Haname's father and Mizuko's husband. He died because a serious illness when Haname was 3.

He met Mizuko in a sword class that she attended just as him.
Daisuke had moved to Namimori with his wife to find a job that satisfied him, going against the wishes of his parents.
After finding a good job, he managed to buy a large house that Mizuko had to sell, after his death, and move to an apartment.