Great hitokiri isn`t he?

From this moment you should get feeling that something desperetly wrong Why not just students, why two?

As i understood this is Hakkei. Martial art about using one`s own life energy (ki) I think this is how Shouyou did this

The key moment is that Oboro did not even touched Gintoki. We have seen some great kicks in the manga but I can remember something really similar only once

Oboro moment was in 259 episode I think and Katsura`s in 110. I usually don`t trust anime very much but I think this was done right. Zura did not touched his opponent (Shachi)

I have not read Rurouni Kenshin but I know that in 165 chapter he is thanking people for checking bodies after him, Which brings a question about how does Katsura knows what needs to be done in this situation? Similar question to this moment

Long story short I think Katsura was hitokiri. Hitokiri for Naraku. That explains why Oboro used numbers. Not only he has seen one student, he has worked with him