I put together some elemental reactions for a 5e one shot based on Genshin Impact. Every character was assigned an element and gained the Apply Element cantrip. I’d have added in Acid damage as Dendro, but what I made here covered all the players and enemies. Didn’t bother with Geo. Oh, and any special attacks/damage spells the characters used applied their element in addition to the normal effects, causing major reactions. Apply Element only causes minor reactions.

Apply Element

Evocation cantrip

Casting time: 1 bonus action

Range: 60 ft

Components: S

Duration: Instantaneous

You direct elemental energy to a large or smaller creature or object within range. The target is surrounded by the caster’s attuned elemental energy. Elemental reactions caused by this will have only minor effects.

Elemental super effective cycle Electric -> Water -> Fire -> Cold -> Electric

Reaction list: (CON and DEX indicate a save based on caster’s save DC)

Water + Electric (M): CON Lose action

Water + Electric (m): CON Lose reaction

Water + Fire(M): Blinded/Half damage

Water + Fire (m): Disadv on next attack

Water + Cold(M): CON Stunned

Water + Cold (m): CON Move - 15

Electric + Fire(M): DEX Prone + 10 knockback

Electric + Fire (m): DEX Prone

Electric + Cold(M): CON -10 AC

Electric + Cold (m): CON -2 AC

Fire + Cold (M): Double damage

Fire + Cold (m): Extinguish/Melt element

Thunder + Any (M): Remove element, spread

Thunder + Any (m): Remove element

I have a half written FATE campaign that starts off with making the players thinking it’s an isekai until about session 3 when I corner them with enemies, play this, and give them their I am thou, thou art I speil; surprise you fools you thought it was an isekai deconstruction but it was Persona the whole time!

I loosely adapted Paper Mario: The Thousand Year Door into 5e. Very loosely; I didn’t take any of the places or people, but I did the overarching “go find these lost relics so we can stop the world from ending” thing. I think it went well.

My advice would be that the only canon that matters is the one that you build with your players at the table. Use your inspiring source material as the starting point, not the sum total of your game.

This is the memes community. You’d probably get better results posting in https://ttrpg.network/c/dndnext or https://ttrpg.network/c/askgamemasters (You might want to subscribe to those communities as well)