There’s not really any such thing as a “playful” knife fight, not when it comes to live weapons.
Live weapons are what we call real knives, rather than practice weapons
or fake knives.
It’s also a terrible idea to do this without any sort of
protective gear. Now, there are definitely real world idiots who will
do it and call it “fun”. They are the same real world idiots who often
end up as cautionary tales on the six o’clock news. It’s also how bad
things like stab wounds happen, people get injured, and/or die.
You’ve basically got two idiots actively trying to cut and stab each other. Even if they’ve got some kind of pact to avoid the truly vital areas, someone is going to the hospital when this is over. And that’s just if nothing goes wrong.
Initially, if you know nothing about weapons, you might assume, “Well, that’s not that bad. They do that sometimes with swords, right?”
Knife combat is faster than sword combat, it happens in a range that is much closer to your body than sword combat, and has a lot less margin for error.
You can deflect a sword with a sword.
You deflect a knife with your free hand.
Playing with knives is a lot like playing with guns. While some of the other weapons like swords and staves will give you some room to mess around, knives don’t. All live weapons are deadly, but the major issue with the knife is that there isn’t much blade so it limits your options on what you’re aiming to hit.
While swords have the capacity to block and deflect with the blade itself, all knife strikes directly target the body and the deflection comes from the free hand because knife combat is supplemental to hand to hand. It happens in the same range as a fist fight. If you want to imagine what that’s like, think of your favorite fight scenes with fists.
Now, imagine the same thing happening if they’re holding a knife.
Knives are not toys.
The short answer is: they’re playing with real weapons and those weapons have a live edge. You never want to play with weapons because, even in the right hands, weapons are dangerous. The difference between someone who knows what they’re doing and someone who doesn’t is the understanding of just how dangerous a weapon can be. All the safety rules still apply with a gun, whether you know how to use it or not. Any mistakes made can end up costly, especially if your characters run around like chickens with their heads cut off afterward because a mistake happened and no one is trained in first aid.
So far as I can tell, there’s a mistaken impression on the internet about dangerous objects and skill sets where people believe that if you reach a certain skill level then mistakes don’t happen to you anymore. It’s the same problem that a lot of very skilled real world people have where they assume that because they know the rules, they can break them. This does or doesn’t apply on a case by case basis and the difference between who is smart and who is dumb often boils down to respect.
The dumb person believes that because they understand how knives work, knives can no longer hurt them.
The smart person understands that no matter their skill level, knives are always dangerous and mistakes can happen even under controlled circumstances.
One becomes reckless while the other cautiously takes risks.
So far, your characters are working in the first category.
Good enough to know what they’re doing, dumb enough to think they’re gods.
This is the perfect headspace for them to be in if you want one of them to die.
When working with live weapons, one behaves under a very strict set of rules because it is very easy to hurt yourself, your partner, or some fool who comes flying in out of nowhere.
I could see your setup actually happening. I know exactly how dumb some people can be.
What’s most important for you to understand if you’re going to do this scenario is that every single character involved made a catastrophic error in judgement and that they are all idiots.
The two who decided to fight with live knives are morons.
The one who decided that the best solution to stopping them was to jump between them and their very real weapons is just as stupid. If they are the one who dies, then they honestly had it coming.
It breaks every single safety rule. It’s very dramatic, but it heightens the danger in the situation. People will do it. Still, it is so dangerous that they usually get hurt and getting stabbed is way worse than a punch in the face.
These two shouldn’t be “playfully” fighting without supervision anyway, but again people are stupid. The less knowledge they have, usually the dumber about it they are.
In an allegorical, real world story, a friend of Starke’s once came home to find his roommates duking it out with a fire axe and one of those cheap dropforged katanas.
My martial arts instructors, who should’ve known better, allowed two underage black belts to spar with the old UFC gauntlets from the early 2000s that had fiberglass inserts to protect the knuckles. The end of that story is my brother nearly lost an eye when the other boy’s punch connected solidly enough to crack open his eye socket.
Starke knew a black belt in karate who told him a story about how two other instructors weren’t paying attention when they let some lower belt levels free spar. The end of that story is they both kicked each other and broke their legs.
My dad once went off a ski jump while buzzed and fractured his leg in seventeen places.
Humans have the capacity to be really stupid, especially the ones who should know better.
You don’t have to stretch that far for a character to do something stupid and that stupid results in someone hurt or dead.
However, when you take this tact, you have to accept is that it’s the result of stupidity. This isn’t some accident that no one could’ve predicted, it isn’t a tragedy that came out of nowhere. It happened because these characters were engaging in unsafe practices and taking unnecessary risks. Everyone in this situation made serious errors, especially the one who decided that jumping between the two characters with weapons was a good idea.
So, yes, it’ll be tragic. However, it’s important to recognize the difference between the tragedy that is unexpected and the one which is predictable. This is the kind of tragedy you can see coming with bells on.