Shonen anime is defined by many things: spiky-haired protagonists, the power of friendship, but one of its most prominent features is a power system. A power system is simply the rules and expectations attached to characters’ abilities in the story, usually a type of power that most of the characters can use. They can adhere to any number of laws or none at all, and it’s more of a story device than a convention exclusive to anime.

Within writing, however, there are multiple kinds of power systems. Brandon Sanderson, author of the Mistborn series and many others, has written extensively on magic systems in literature and how magic can and should be used to tell a story, and coined the term magic systems. He’s actually written a lot about it, and while I’d love to go in depth about all of his laws of magic and how they’re presented in anime, right now I’m here to get into how magic systems play out as shonen superpowers.

To oversimplify egregiously, a hard magic system operates in expected, predictable ways, and strict limits on what they can and cannot do. One of the best examples in anime is Fullmetal Alchemist Brotherhood, moreso than the 2003 series. The laws of alchemy are absolute and the punishment for violating those laws is harsh and immediate, and the defiance is rarely successful.

Then there are soft systems, where the rules are flimsier and the viewer or reader’s idea of what the characters can do is much vaguer. A good example would be something like Lord of the Rings, where you’re left with the impression that Gandalf is immensely powerful, but you’re not sure what he can’t do. Soft magic systems aren’t worse than hard ones, or vice versa, they’re just intended to tell different kinds of stories.

Fullmetal Alchemist’s characters are scientists who are working within clearly defined boundaries, so it makes sense that their problems can only be solved through logical and thoughtful use of their toolkit. Lord of the Rings, on the other hand, are books about good persevering in the face of evil, so it doesn’t need to establish rules on what the One Ring is capable of, or what Gandalf needs to do to create a powerful spell or a moderate one. To explore these concepts in greater detail, I want to highlight a hard system, a soft one, and one that rides the line.

Jujutsu Kaisen’s jujutsu sorcery and manipulation of cursed energy is a hard magic system with a lot of creative applications and room for unique abilities. People naturally produce negative energy when they feel hate, sorrow, or rage, and that in turn produces cursed energy. Clumps of cursed energy can become Cursed Spirits, while people who use cursed energy to exorcise curses are jujutsu sorcerers. From there, many people or families have individual abilities called Cursed Techniques, which could be any number of established powers, or a new one entirely.

Cursed energy also has a tendency to be determined at birth, and there’s not a lot you could do about it. Yuji Itadori can punch real good when he’s mad, but Satoru Gojo can level a city in the first half of the afternoon and still get home in time for dinner because he’s just born with more cursed energy. Not fair, but the series is frank and reveals early on that about 80% of a sorcerer’s potential is innate. JJK really doesn’t care if you want to pull yourself up by your bootstraps.

Cursed Techniques aren’t the hardest form of magic, because they’re all individual powers might have their own rules, but not any broad laws governing every technique. Aoi Todo’s ability to switch places with someone by clapping might be limited to two hands slapping together, but it doesn’t even have to be both of his hands, as demonstrated by a high-five. No, things get more complicated with the introduction of Binding Vows, and Domain Expansion.

Binding Vows are exactly what they sound like; the sorcerer makes a promise and receives something in return for it, with vague consequences for not holding up their end of the deal. Where vows become interesting is when someone like Kento Nanami, ever the salaryman, makes a Binding Vow to limit his cursed energy during his 40 hour work week. When he goes into overtime, his investment is paid back several times over and he becomes stronger than he would normally be because he put a limitation on himself. Likewise, revealing your cursed technique to your opponent gives a similar buff, at the cost of losing any chance to surprise them.

And the ultimate move of any sorcerer or Cursed Spirit, Domain Expansion, is a beautiful case for how giving magic rules and limits can make something so much cooler. When someone performs Domain Expansion, they create a pocket dimension out of cursed energy where they are perfectly in their element, think the reality marbles from Fate. The volcanic Jogo’s domain is made of molten rock, while the dramatic and old-fashioned Sukuna’s domain is a traditional Japanese shrine built on the bones of his victims. The first and foremost rules of a domain is that only powerful sorcerers can use them, and any hit made by the user is guaranteed to land.

Domain Expansion is intended to trap your opponent so you can get your all-out attack in on them, but there’s drawbacks. It’s nearly impossible to break out of one, so if someone tries to break in, it’s quite easy. Then, there’s also the risk that your opponent will attempt Domain Expansion, and it becomes a simple game of who has more raw power at their disposal. The stronger sorcerer will automatically push out the weaker domain, and you’ve wasted your best hand and essentially put yourself at their mercy.

JoJo’s Bizarre Adventure has a lot of different power systems across its eight parts, but they all generally are soft magic systems that unconvincingly pretend to be hard systems. If you’re unfamiliar, the first two parts of JoJo, Phantom Blood and Battle Tendency, use the breathing technique hamon to fight. Hamon conducts the power of the sun, and both Jonathan and Joseph fight vampires or vampire-adjacent creatures that are weak to the sun. Meanwhile, from part three on, the Joestars fight with Stands, astral projections of someone’s fighting spirit that usually have a special power, as well as being able to punch real good.

Hamon is remarkable only in the sense that it does whatever the plot needs it to do, like how Joseph could make a ladder out of falling icicles to avoid plummeting off a cliff. Apparently hamon also generates infinite friction between objects, which is also how he and Caesar are able to scale a sheer pillar covered in oil by conducting hamon through their fingertips. We know it conducts certain materials well, like oil, water, cotton, and also swords if need be. Hirohiko Araki is nothing if not creative.

Stands, conversely, have a handful of rules that they actually abide by most of the time, but it’s nowhere close to a hard magic system. Most Stands are considered “close range” and lose strength depending on how far away they are from their user. Some long range stands can be meters or even kilometers from their user without any adverse effects, like Kakyoin’s Hierophant Green, but they usually trade their power in exchange for that distance.

These rules can make the fights in JoJo more interesting, but you know that Araki would never bind himself in regards to what a Stand User can do. Star Platinum’s powers are strength, speed, and precision, to the point where it can pluck a bullet from the air with two fingers. If you could explain to me how Star Platinum can extend its finger many times past its normal length with tremendous force using only those powers, you’ll spare me a trip to the asylum because Araki won’t answer my calls.

There’s this general idea that Stands can manipulate their form like that, but it is used so rarely that it can generally just be seen as a deus ex machina. Hierophant Green and Silver Chariot are shown to shrink down to go into a human skull, but once they defeat the Stand inside that skull, they never do it again. Sure, Polnareff says it is hard to maintain the small form and manipulate the Stand, but he could literally become a world class brain surgeon with that. Forget Dio, Polnareff could essentially cure brain cancer with small Stands, and he just gets tired and decides not to.

There’s more to JoJo than just hamon and Stands, like the Spin power in parts seven and eight, but I haven’t gotten around to even finishing my retrospectives on the parts that have been animated, so I’ll leave it at that.

My Hero Academia’s power system takes a bit from both hard systems and soft, as humans are born with innate powers called Quirks. Most Quirks are physical abilities with physical properties, so naturally they have limits like anything else a person can do. However, most people could tell you that great duress increases their physical prowess, like how a mother might be able to lift a car off of her baby. My Hero Academia even explains that most people mentally handicap themselves to avoid causing their body undue physical strain in every day life.

Take for example Bakugo’s Quirk, Explosion. He sweats a substance like nitroglycerin, which he can combust from his palms to produce massive blasts. Now, Bakugo’s Quirk is naturally powerful and he has a resistance to both the burns that his Quirk would inflict, as well as the hearing or lung damage that constant close exposure to explosions would cause. However, it is shown that when he uses it too much or in rapid succession, it puts a lot of stress on his body. It’s the same as any physical exertion like exercise; you can stop and catch your breath, but you can also push yourself well beyond your initial breaking point.

Likewise, most Quirks come with natural drawbacks. The Flame Hero, Endeavor, wanted to overcome his weakness to overheating in a fight, so he purposefully married a woman with an ice Quirk to produce a child with access to both elements. This child, Shoto Todoroki, doesn’t have to worry about being overwhelmed by his heat or his ice, because he can always moderate one with the other. He wouldn’t be as powerful if his Quirk didn’t create this feedback loop.

Almost every Quirk has properties that treat them as actual extensions of a person, because if Uraraka can make things float, obviously she would get nauseous while floating due to shifting to zero gravity. Iida’s engines in his legs are prone to stalling, overheating, and everything else that afflicts engines in the real world. Tying the power system to a person’s physical abilities is actually a clever way of allowing bursts of progress while still feeling earned.

I want to make it clear that no power system or combination is better than the other. The purpose of a power system is to give fights and character abilities a framework, and that frame should vary depending on the kind of story being told. A show with high stakes that takes itself seriously would benefit from a rigid magic system, while a book that is more focused on world-building or its plot might steer clear of putting all its attention on how magic works.

There’s also a lot of advantages to making these rules in general, just so that when you break them, it makes for a bigger impact on the audience. Demonstrating that Deku has to break his arm in order to throw a punch means that when he punches without hurting himself it is a big deal. You can’t take big attention grabbing moments like that for granted when your reader could set the book down at any moment and never pick it back up.

So if you’re trying to implement a magic system into your book, your manga, or any other creative project, the first thing to consider is how it serves the story. It seems obvious to say that the elements within your story should contribute to the work as a whole, but it’s easy to forget. Some people like to put pen to paper and build a whole world and four magic systems only to forget that these devices are meant to push your characters and plot into new and interesting places. The absolute best writing advice you could get is that every part of a narrative should fold over each other until they create a whole and cohesive narrative.