Is it plot shenanigans?

[SweetDao]

Well, hmm, basically there is this ability.

It's able to "change the user backstory" and change all of his skills accordingly. That's all we get in the manga.

For a more lengthy explanation, in the novel, it's described as the following:

[Post-set Surprise]. At the time of use, it retroactively acquires settings such as “was actually the enemy's anti-existence” or “was actually the only counter-weapon,” and reacquires all of its skills as if they were special effects skills for the target.

As an example of use, there was a creator God that was "The First Light" and boasted that he's invincible and the only being capable of killing it is "The First Darkness". Therefore, after using this ability, the character transformed all of its skills into "The First Darkness" version of them while also becoming such a being.

Obviously, it's adaptation, but I wonder if that could be some sort of plot stuff too.

 

[KingNanaya]

yeah, sounds like plot

 

[Fixxed]

Plot it weird and overrated ability, basically you need some meta fiction proof for it being a plot, if you dont it are a fate manipulation at least (well all plot are fate essentialy)