@prstone https://i.postimg.cc/gz0hdTSw-/if-only-there-was-a-mirror.png
"If only there were a mirror around here so that I could check."
Please inform the proofreader that this is incorrect grammar. "Were" should be used only with plural nouns. An exception is the word "you," which was originally plural.
The flawed sentence would be correct if rephrased to refer to multiple mirrors. "If only there were some mirrors around here so that I could check." If there's only one mirror, then you must use "was" for the grammar to be correct. "If only there
was a mirror around here so that I could check."
I saw a similar misuse of "were" in the previous chapter, as well.
https://mangadex.org/chapter/1113341 "If it were that easy, I'd already have had energy blade long ago." The word "it" is singular, so it should be written as, "If it
was that easy, ..." To make the use of "were" correct, then it would have to be written as "If they were that easy, ..."
For deciding between "was" and "were," it's all about singular versus plural.