By kneading senjutsu chakra, Fukasaku's long tongue gains utmost solidity and sharpness. It then leaps from his mouth with tremendous speed and force, even tearing a hole through bedrock and metal pipes. With that ground-splitting power, the enemy is cut in half. The way that both the enemy and the ground itself are cut apart is reminiscent of the strike of a great sword.
"Zessen" is written with the kanji for "tongue" and "battle". It can be translated as to "battle with tongues". In normal use, however, it means "war of words", or "verbal dispute", in reference to Fukasaku and Shima arguing all the time. The full kanji can be translated as "War of Words Slash".
In the anime, colourised manga, and various video games, Fukasaku is depicted firing a highly pressurised stream of water from his mouth, rather than extending his tongue.