Unlike the authors of the previous opinions here, I feel okay when the translator has a larger-than-usual whitelist of Japanese words he's willing to leave as they are (not translated) in the text.
We all know how it usually goes:
① Honorifics such as “-san” and “-kun” and “-sama”.
② Semi-honorifics such as “-senpai” or “-sensei” even when one of them becomes a separate word (an
addressee, a word to name some person), like the capitalized “Senpai” in
mirror moon's translation of “Tsukihime”:
③ Memes or terms of Japanese origin such as “chuunibyou” or “denpa” or “dosanko” or “freeter” or “menhera” or “NEET” or “oshi” or “otaku” or “yandere”. (For example, in
StoneScape's translation of “
Otaku ni Yasashii Gal wa Inai!?” the Western word “fave” was used to translate “oshi” in the 47th chapter at first, but later the readers forced StoneScape to leave that word untranslated in the alternative version of that chapter.) Personally I even feel that a Japanese “gyaru” is not just a local version of a Western “gal” and that we should treat that as a loanword that changed its original meaning.
④ Specific expressions of politeness such as “itadakimasu” or “ojamashimasu” or “yoroshiku onegaishimasu”.
⑤ I am okay if the gender-neutral word “Maou” is used as the title of the King of Demons (or of their ruling Queen), especially if originally it's a plot device for the humanity's hero not to know whether a king or a queen is the final opponent.
On the other hand, the translator may fall in a trap when decides to use the word “demons” too soon to name the evil magical beings (originally “mamono”) because then the same word cannot be used on sentient magical beings (originally “majin” or “mazoku”), and if the word “devils” are used to name those ones, then the translator is baffled when finally some demonic evil beings (originally “akuma”) appear as a separate opponent.
I'd rather prefer the RPG tradition of using “monsters” / “demons” / “devils” for that progression, especially because it allows the name “the Demon World” for the realm of origin for the “demons” (originally “makai” for the “majin”/“mazoku”).
I haven't read the raws but I have a lingering suspicion that here the “the demon forest” should be “the forest of monsters” in that sense.