I'm pretty sure Togame plans on keeping Shichika to herself, as evident from her actions when he was with Zanki. Also, the wielder does not necessarily need to be willing to do anything to keep the blade to be "poisoned". Zanki fought on equal terms with Shichika even if it put her on a definite path to losing. She even let go of the sword willingly after admitting defeat herself. Konayuki let go of her sword too.