
So he's planning on marrying her then killing off her family?

He hates heroes because of the corrupt heroes and hypocrites. He considers his in law families the same. He’s not going to change his objective of killing heroes but I think he will reconsider killing his in laws in the future considering he only goes for the corrupt and bad heroes and people. As of right now the in law hero family is protecting the hero association kind of and that’s getting in the way of him eliminating the hero council which is filled with corrupt heroes. I believe his motive is to get rid of the in law hero family so that he can finally get to the corrupt hero council because the in laws are protecting them especially since they were the ones who made that council (the in laws don’t know that the council is filled with corrupt heroes I think just that some of them are annoying?)
Kyosaka-san