When reaching the top of Ashina Castle and confronting Genichiro (cutscene):
Genichiro: How is grandfather?
Emma: Lord Isshin is... it's a wonder he is still with us. A miracle.
Genichiro: ...is that so. Divine Heir, I'll ask you once more. Accept me into your immortal oath.
Kuro: I cannot do that, Lord Genichiro. Your victory that day means nothing. He will risk his life to take me home. For he is my shinobi.
Sekiro: My Lord, I have come for you. This... will only take a moment.
Genichiro: I see. For as long as you are alive... The dragon's blood can never be mine.