I enjoy watching students practice the Kanshiwa Bunkai. Being someone who encourages thinking outside of the box (as mentioned repeatedly in my youtube videos), I would like to offer an alternative approach on doing this bunkai. For the folks who are already doing it, please let me humbly say-- bright minds think alike

Typically: The defender stands in the middle facing three opponents, one to his left, one to his right, one in front. He blocks and punches to the left, then to the right, then to the middle, then---, movie style. The opponents patiently waits for his turn. Think about it.
OK, it is only a dojo training for beginners some might say, but, I suggest we train everyone realistically. This specific "typical" approach may not exactly ingrain the right idea on defending against multiple opponents.
In a real self defense situation, the defender would be lucky if he could finish the first punch before being attacked or taken to the ground by one or both of the other two.
Of course, no one should even try to defense against three thugs, no matter how good he is--- but if push comes to shove and your own safety or the safety of your love one is in jeopardy, may be you are stuck without options.
So, let's train properly, and the Kanshiwa Bunkai is excellent for training against multiple opponents, even if we have to follow the kata movements for the sake of doing a bunkai.
My suggestion: From the middle where you face the three opponents, maneuver yourself to be in line with the three thugs so they are one in front of the other and blocking each other. The hope is that the other two will be blocked by themselves while you are taking out the first thug.
Let me emphasize here. Never practice ineffective or whimpy strikes or they will be ineffective and whimpy when you need them. In this situation the strikes must have knockout power. You only have one chance. Since there are three of them, you probably do not want to punch his head either. If you break your knuckle -- well---, hope you can deal with the rest with one hand. But the kata uses fist strikes here, so, go for his groin. Boom!!

In your bunkai practice, after striking the first thug, go after the second in line and make sure he is blocking the third, then go after the third.
To continue with the kata movements, you then maneuver to side kick the first one, at the knee or behind his knee with the goal of breaking; then maneuver to side kick the second thug at his knee, then the third. Then, you can play with the rest of the kata.
By the way, for the sake of at least this bunkai anyway, let's practice the Mawashi-uke (circular block with palm strikes) with the higher palm strike to the opponent's face/nose area instead of the side of his upper chest. I have no confident with my strikes to anybody's chest but that is just me the little guy talking. No time to be nice when dealing with three thugs who are attempting to really hurt me here so I will aim to break his face.
The point is, practice as realistically as possible.