This MU chart was created through personal experience and feedback from both sides of the MU from other community members, however this is still purely subjective so take it with a grain of salt
Asuna mirrors are silly because you both are feeling each other out with her normals, repositioning yourselves constantly and aiming to get a good snipe with Celty 5S (assuming both Asunas are running Asuna/Celty). We have the thought that Asuna is pretty “honest” but when we play a mirror we kind of realize how annoying we truly are.
Asuna primarily wants to continue being oppressive with her fast mobility and normals and continue to apply setplay pressure. These characters have a tough time taming her and keeping her locked down. While it is possible through assist selection, the kit of these characters don’t offer much to make an Asuna hesitate in their gameplan.
While not quite as advantageous as the previous selection of characters but also not quite as “even” as the next batch these characters have a form of minor aspect that puts them at a very slight disadvantage but not enough that I would call it a “bad match up”. Asuna can deal with the zoning offered by the characters listed and the speed of her normals/mobility can out those of Selveria and Kirito. Rentaro is a special case because in trump he is faster than Asuna however once caught in setplay his trump works against him making him eat more from Asunas gameplan. His gameplan isn’t so consistent as others putting him at a slight disadvantage.
These characters can compete with Asuna on equal terms whether it be through having equal or better mobility then Asuna, having better ranges normals but slightly slower than her, offer better setplay or other small aspects. They can work around her setplay gameplan pretty well however does not mean they are completely immune to it.
Asuna’s greatest strengths are through her strong normals and setplay gameplan through a strong well balanced character however will show weakness to those who go a bit beyond balanced well retaining stronger normals and a stronger gameplan than her own. Not only this Asuna isn’t exactly an explosive character, other characters can be explosive given the right conditions however these MUs can be less forgiving in comparison.