Nuki. I.e, the blur-like crescendo at the end of the piece. Strike the bachi down, then in almost instantaneous succession, preform two hajiki (?one with the ring finger and the other with the index). Preform an upstroke and repeat the two hajiki.
Advanced: The Index finger sounds the thin string (san-no-ito) while the ring finger sounds the thickest string (ichi-no-ito) to “ignite” the sawari.