You idiot 2

If I marry you, then that means you'll become my sister's younger brother, right?

Well... I guess that would be the case.

But it'll be weird to have a younger brother who's actually older than you, huh...

As for me...

...I'd rather want you to be her big brother, though.

For you to worry about your little sister like that... You're such a kind big sister, Jougasaki-san.