Henka is a Japanese noun that has a group of possible meanings including 'change, variation, variety and inflection.' Where it applies to sumo it takes an even more specific meaning, "sidestepping."

A henka is a much frowned upon manoeuvre that occurs at the tachi-ai, the initial charge at the very beginning of a bout. Anyone who has watched any sumo will know that the two wrestlers typically clash head-on. When a henka occurs, one of the wrestlers deliberately steps to one side. This usually means that the other wrestler charges into thin air and is generally defeated either through a katakikomi (push on the shoulder or back) or by simply falling flat on his face. It is not illegal but you can see how it is unsporting.

Henka usually occur amongst lower ranked rikishi who are either desperate to break a losing streak or who are on the brink of achieving their kachi-koshi (more wins than loses) and just want to get over the line. Lately though more senior ranked wrestlers have been indulging, notably the ozeki Takakeisho. During his bout with Hokutofuji, when he pulled the henka, the audience was notably silent at the end, signalling its disapproval.

Things do tend come around though and the following day he ended up on his stomach after Wakatakakage (for it was he) did the same thing to him. I am wondering if one day the henka becomes illegal, given the fact that it so often is considered below the belt in what is upheld as a noble sport.