By the time we come to Kahak, Fushi has seen the life and death of a dozen such descendants. (Keeping in mind that the succession tends to skip generations: Hisame was the first successor, but the third generation, Oumi never became a successor in the fourth generation, her daughter Ushio became the second successor in the fifth generation, her daughter in the sixth generation was skipped, and Chisui became the third successor in probably the seventh generation, etc.)
Most likely, each and every one of them has come on to him and asked to make a child with him. (Because they've been taught that this is the secret goal of their entire family, because their ancestor Hayase was the first to spread the divinity of Fushi, and that means they should be the first to join their lineage with such a supreme being.)
Just look at some of their faces over the years - some of them seem to be truly adoring, utterly enchanted, entirely ready to embark upon an epic romantic relationship, as if they were born to meet Fushi and bear his child. (And they really were, if you take Hayase's records seriously.)
Most likely, each and every one of them has dutifully reported their progress, such as how many people were saved, how many Knockers were destroyed, how many people learned to defend themselves, and more. It wouldn't be unlikely that Fushi knows the entire history of their organization, especially if any of those girls was persistently chatty, or tried to impress him, or wanted to get closer.
Based on the succession of leadership every other generation, and with Kahak as the sixth successor in probably the 13th generation, it is nearly 250 years after Hayase. (If you assume that each generation produces a female child at the age of 20.) That's 250 years of people coming to you to say, "We're doing good things in your name." That's 250 years of people saying, "I like you. I love you. I want to have your child." After 250 years, you'd expect Fushi to have gotten used to the Defense Corps following him around, and the Hayase family's boy-crazy antics.