I'm kinda skeptical about this part in the Perfect Memento – 巫女が勝つまで繰り返され、一旦勝負が付いてしまえば遊びはおしまいである。

TH Wiki interprets it as Reimu liking to have rematches until she scores a win. But the sentence definitely paints a different picture. Akyū here is saying that the matches repeat until Reimu scores a win; and once the victor (within the same sentence, that would logically be Reimu) is decided, then the game is over.

Wait a minute... I think... isn't this last sentence referring to incidents? The phrase by itself doesn't say what is repeated, and the previous sentences are not talking about spell card duels anymore, but incidents. Which means this is a way of saying that Reimu must continue and persist in resolving the incident until she scores a win and put that incident to an end.

Which means the "game" here does not refer to an individual spell card duel, and the sentence is basically saying – "The incident continues until the shrine maiden claims victory – once a resolution is reached, this game comes to an end."