More than anything else that remains to him in this world--more even than his hope of the Grail--Acht believes in Larasviel's loyalty to her family. He has written the coding in her heart, and he knows every sigil and syllable; he knows what she will choose, when she is made to choose. Therefore, he speaks with the certainty of a man repossessing stolen property when he says, "Then let her decide whether she will go with me to the Einzbern base, or stay here. I will abide by her choice."