Because there haven't been a proper guide post for this particular part, here we are: Quick Swap.
For those who are stuck at the "Quick Swap" tutorial: first of all "quick swap" here only means "the next action(s)(?) will not consume a turn", not "switching to your side arm because it's faster than reloading".
First, press S, which pops up a quick menu. Then use arrow keys to try your very best to navigate to the "Quick Swap" option, then Enter/Z it. Afterward, press X to enter another (main) menu, and press Q/W to navigate until you see weapons (which should include a gun). Navigate to the gun, select it, select "equip", after which you should see the girl holding 2 guns on both sides.
THEN you must press Q to initiate aiming, press the the correct arrow key to orient the girl, then Z to shoot.
And that's it. Violating any part of this order will (most likely, I don't wanna fuck around yet) result in the bunny getting killed, the tutorial reset, and you are minutes further from seeing the girl getting violated.
Already I can tell this is one of those gems with very bad translations that can really ruin things, especially with its more complicated gameplay. But my dick has enough hardened will and determination to fuck through it all!