Real Jujutsu

Take the GLOG wizard of your choice. Roll a D12 (I'm assuming the wizard you chose has 12 spells it can have, in like a school or something) or maybe a D100 if you're using a list like Skerples 100 orthodox spells: https://coinsandscrolls.blogspot.com/2017/03/osr-100-orthodox-spells.html

That's your spell - your Cursed Technique - it's the only one you get.

You get +1 MD per template, like a wizard, but you don't get miscasts or dooms. At template B your MD return on a 1-4. At template D they return on a 1-5. At template C you get Reverse Cursed Technique - you can spend MD to heal their [sum] (but MD so spent don't return to your pool until the next day) or cast the reverse form of your Cursed Technique - figure it out. At template D you get your Domain Expansion. Also for every MD you hold on to you get +1 to-hit & AC so long as you're unarmoured.

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So put more legibly it'd look something like this:

Equipment: Japanese street fashion
Skills: Kung fu or whatever
A: 1 Spell, +1 MD, +1 to-hit & AC for every MD you've got stored when you're also unarmoured
B: MD return on 1-4, +1 MD
C: Reverse Cursed Technique, +1 MD
D: MD return on 1-5, Domain Expansion, +1 MD

Domain Expansion (領域展開):

Ok did you watch those videos? You get one of those. You can give it a cool name.

To use: spend however many MD you like - you won't get them back until the next day no matter what you roll. The domain covers a spherical volume with a radius of [dice]x5 feet. Your Cursed Technique affects everyone (or everything, depending on the target of the spell) within this volume at the [sum] you rolled, every round they remain within it. Also they don't normally get a save to resist. You can add a condition like "my Cursed Technique won't affect people I'm touching" to spare your allies, but then other people can take advantage of the condition too. You can't revoke the condition later (it's a binding vow, read the manga).

If two domains come into contact with each other the bigger domain wins, unless one domain's effect is lethal and the other is non-lethal, in which case the non-lethal domain wins.

To get a save against the domain's imbued technique you need something like Falling Blossom Emotion, Simple Domain, or Hollow Wicker Basket (read the manga and make up your own rules).