It's because... your mother wears her heart very openly. She wanted to name you something she felt very close to her heart.
[At least, that's what he thinks. He doesn't know much about a daughter with children, or having grandchildren (what is even happening right now), but he thinks he knows Yuuki, from those short years together.
Or maybe she just found them cute. That could be it. It's not the strangest thing he's heard all day.]
I'm happy I am able to meet my grandchildren.
[Please to not be trying to trick him. Haruka's poor heart couldn't take it.]