[Hokuto had gotten used to have to explain it by now between Kamui and Subaru there seemed to be a lot of confusion.]
There's three different Kamui's here, well that I know of, and I only know one of their family names the other two I'm not sure about. But according to the tallest Kamui today is Kamui Shirou's, the Kamui who lives here, birthday, so he threw him a surprise party.