I was going to ask about the blade there. Is it going to be Hanzo steel? LOL...
What I was going to suggest for over all ease of use was this: Cut the blade so it doesn't pass through. You may run into some issues trying to get it to work as planed. The first thing I think of is the hardware conflicting. There's only one real angle to get it to miss everything and pass right through. Some Katana's aren't long enough to get this downward angle to have enough blade sticking out on both ends. This WOULD be cool if the blade was red on the inside, or had a heart or something with the blade going through it on it's way out of the case.
But my idea was to cut off sections. To get it to stick, you could go ahead and cut holes for it to fit in the plastic, and epoxy it in. You can also mix dye's with the epoxy to get it to be a semi-clear red. Clear red looks cool IMO. If you don't want it semi-clear, mix dye with Liquid Nails. I'd still cut holes because just mounting it to the case with epoxy only has one direction it'll hold with. Pulling on it should be fine, but you could wobble it off. With a hole, side angle impacts will also be strong enough for random knocks.
But this colored epoxy may come in nice in the other spots like the bays and the side. If you over apply it, it will flow out in a more natural blood like way. Gotta be careful with this as you could glue the drives shut