Having caught Kuro completely by surprise, Tsunami won, using the reason why she's named after Tanaka Naoki, the Tanaka Thai Kick.
But as was shown throughout the story, what Kuro lacks in intelligence and tact, he more than makes up for in brute power and resilience, the guy survived incineration and several hundreds of thousands of June's cockroaches.
The SD version of Kuro plummeting to a rather painful encounter with the pavement, was to have a little humor in what was very much a very dark scene.
I'm sure all the readers of the "Last Ronin" comic recognize the large panel, it's from part one where the comatose body of that series' version of Karai is looked over by her son Hiroto.