Ok, before I forget, I have noticed 2hat may be a discrepancy.
I am not 100% sure if it is this manga specifically, or all of the isekai manga that introduce Othello, Go, and/or Reversi but I vaguely remember THIS one using more than one of those names (on a cell phone, checking is going to be bleeping difficult, will do later and correct myself if no one else has) anyway, I just double checked and each of the three is a completely different game: Othello != Go != Reversi. (Reversi is actually western if I read wiki correctly, Othello was Japanese or Chinese and Go is whichever the previous one was not, if I read wiki correctly. Please correct me if I'm wrong, again cell phone, hard to tab between websites).
That said, I sincerely doubt that this is Reversi, and wonder which it is... Or if the mangaka/author themselves know the difference... (I certainly didn't)