Shogun Yoshimune was letting his sister know of the great political powers he had, and at the same time reminding her that she could be replaced regardless of whom she thought she was.
He was not going to let any personal feelings which he didn't have, to ruin business for him.
Finding her brother so cruel at this very point, Himiko was devastated.
"Are you going to be so mean to me after everything I've been through?"
Tapping his fingers on the long table, the Shogun replied without a single care in his tone as he made his statement, word for word in a way that she would understand perfectly.
"If you want to remain on that seat alongside with Tammu, then birth an heir that will take over from him."
Shifting his gaze to his Daimyos, he continued from where he had stopped.