Thanks for the translation.
I belive this is chapter 10 or 11 of this entry https://mangadex.org/title/24b306a5-c0a6-4a9a-b1d3-c0e26c633261/danshikou-jk-makoto-no-judan
the author writes 新キャラ回です。(This episode features a new character.) at the description on pixiv so I doubt it's a oneshot