Steak said: Most Youkai kill and eat people. It's something Touhou fans tend to ignore, unless they're making a bad joke.
They talk about it all the goddamn time, but they actually never did it (during canon events).
Yukari gaps fresh dead corpses to the SDM, maybe similar shit happens to the youkai. ZUN is incredibly ambivalent when describing this, and to be honest, he pretty much pussied out since the first Windows game. You remember bosses that pour acid on you if you lose, and endings that involve destroying the whole world?