
tf is a chi?

It is, depending on the stories it is used in. Which is why I said 'generalized, simplified'. I know that there is more to it. X'D
irl definition might differ, but more often than not you see chi/qui used like mana in a fantasy story, used for powering certain abilities. And the lack thereof making you unable to use certain abilities. Which is pretty much the same as mana in different settings.

This isn’t accurate, it’s not just something from a fantasy setting. Chi/qi is considered to be the life force of all living things. It’s a concept that’s used in traditional Chinese medicine and martial arts. It’s more of a philosophical/cultural belief and people do talk about it in non-fantasy/everyday life.

I'm not gonna accredit realism to something that's used in the same way as grinded tiger penis pulver to 'cure' impotence or whatever. Sorry. ╮( ̄▽ ̄)╭ Believing something doesn't make it real. And we ARE talking about stories that use chi/qi more often than not to fly on swords, shoot fireballs, etc.. Pretty sure we can agree that's not real. And it being real or not wasn't ever part of this conversation anyway. XD
Ultimately it IS factually used exactly like mana in a wizard story. You can check with pretty much any comic, novel or live action for this. I have seen ALOT, hence why I chose mana as reference in the first place.
Whether people believe in this stuff irl or not doesn't matter. Nor if it has nuances or more details or works slightly different here and there.
How it's used in stories is still done the same as people would use mana, chakra and whatnot in fanatsy stories. Many of which are likely based on the ancient make-belief ideas of some religious aspects, mythologies and so on.
Again, we're talking about the use in stories here, not real life. So there being nuances and belief behind this for some people irl really does not matter in how it's ultimately used/depicted in these fictional works.

Ok, but there’s no flying swords, shooting fireballs, etc. in this story. Chi is not only used fantasy settings and does not always mean some sort of magical power. In a more realistic/slice-of-life/sports genre, you can have characters who believe in chi regardless of if it actually exists in the universe because it’s reflective of what some people believe irl, just like you can have characters that believes in shooting stars, lucky rabbits foot, Jesus, Buddha, etc. and it wouldn’t be a fantasy story. The way it’s depicted in this story seems like the MC is superstitious enough that he believes the ML took away his chi, not that there’s some fantastical power that actually exists in the universe of the story that you use to power up.

That's precisely why it doesn't work for me tho tbh.
If they at least went with a full on magical storyline I wouldn't have an issue with it, but bringing in this sorta thing at RANDOM, mind you, while previously not introducing the world as a 'we believe in this and that' setting, was just not really something I can vibe with.
It's too random, completely needless unless they did it purely to create specific situations (which was likely why they picked it) and it did not enhance the story. It just worked as a plot device, didn't fit into what the story was introduced as (or the lack thereof) and so on.
Things like these need to be properly introduced or prepared to be a thing in a story. Otherwise it simply doesn't work.
People believing something irl has nothing to do with it, again. Especially not since these stories will not work for the handful of people who believe in this stuff and think they are gonna read a story about exactly that or expect all stories they read to have it be a part.
But again; none of this was part of the original conversation.
I wanted to see the threesome tbh. .... >_<