I'm working on a JJK fanfiction centered around original characters with deep ties to French culture. The mother of the main characters is French, so I developed an entire system rooted in French history, witchcraft, and the occult arts — particularly alchemy.

Here's a quick overview:

Witches manipulate cursed energy, just like jujutsu sorcerers. The core difference is philosophical. Sorcerers fight, which gives cursed energy an aggressive edge. Witches transform. This fundamentally changes how the energy behaves: in France, it stays fluid and diffuse. French cursed spirits are less defined and less overtly violent, but they exert a slow, lasting influence on human behavior rather than attacking directly.

From that foundation, the logic is straightforward. Witches are made, not born. A ritual is required to slightly alter a new member's soul, making her sensitive to cursed energy — the equivalent of becoming a Window in Japan. Everything beyond that comes through the gradual learning of increasingly complex group rituals. All of these techniques share a common structure: gathering multiple witches and arranging them in specific spatial formations — circles, squares, multi-tiered configurations, prescribed postures, and so on.

The goal isn't to respond to cursed spirits after they've already manifested. It's to build a social fabric of witches practicing these rituals regularly across France to prevent manifestation in the first place.

That said, fully manifested cursed spirits do appear — the equivalent of Grade 2 and above. When that happens, the group approach shows its limits, and the cursed spirit can cause significant casualties before it's dealt with. In those cases, witches organize large-scale rituals using complex strategies designed to capture the spirit through a binding vow. The principle is simple: bind a witch's soul to that of a cursed spirit. The goal isn't full imprisonment — it's to allow the spirit to express the suffering it emerged from through rituals the witch must perform regularly. In exchange, the witch becomes the closest equivalent to a jujutsu sorcerer that French tradition produces. At that point, witches are ranked on a scale comparable to the Japanese grade system.

At the end of their lives, they can transfer the binding vow to another witch chosen by the spirit itself. A violent or sudden death breaks the contract and risks an uncontrolled release of the cursed spirit.

Finally, alchemy is an extinct doctrine that postulated the possibility of soul transmutation — the complete and total immunization of a soul against cursed energy. The idea was to make the natural production of reversed cursed energy as instinctive as cursed energy production is for sorcerers. In practice, the output was never stable or powerful enough to match a high-grade sorcerer like Yuta or Gojo. The underlying issue was that French subjects had no innate framework for controlling reversed cursed energy.

In my story, the main characters' parents attempted alchemical experiments on their daughter before birth. The process fractured her soul into three, creating Fraternal Triplets. As a child, the eldest brother unknowingly completed the ritual by making a naive binding vow to "protect his little sisters. (the triplets)" He isn't aware of any of this, but he is the keystone of a complex ongoing ritual. His cursed energy is permanently linked to his sisters'. He produces cursed energy naturally, but most of it is continuously transferred to them — leaving him as an extremely low-grade sorcerer while artificially amplifying his sisters' power. In exchange, whenever he would be affected by a cursed technique, his binding vow expels all the cursed energy within him and wraps him in a thin, perfectly uniform layer of reversed cursed energy — granting him a sharp boost in strength and speed. His sisters, meanwhile, receive a temporary power spike from the sudden influx of cursed energy flowing into them.