When in his short story “In a Bamboo Grove”, Tajomaru confesses to killing the samurai when in fact he probably didn’t?

From the text:

Tajomaru’s Confession

I killed him, but not her. Where’s she gone? I can’t tell. Oh, wait a minute. No torture can make me confess what I don’t know. Now things have come to such a head, I won’t keep anything from you.