To Shishou, Nanahoshi-dono is probably like a sister.
I wonder why I did not notice.
Although Shishou also has real little sisters.
In particular, how Shishou interacts with Nanahosi-dono and his sisters, I think it seems very similar.
There are slight differences, but still it's very similar.
The way he watches over them and, if something happens, comes to their aid, it's very similar.
For Shishou, taking care of Nanahoshi-dono is like cherishing his sisters.