Starting with the hammer, GB went 2-0 up in the first end and 4-2 up in the third, before a five-point steal in the seventh prompted their opponents to concede the match.
With that effort in the seventh, Team Muirhead once again got their names in the record books, equalling the highest number of points stolen in a single end of an Olympic fixture since curling, in its current format, was introduced to the Games programme in 1998 - matching a feat that Canada's men are the only other team to have achieved.
Earlier this week, Muirhead's rink set a new Olympic record by notching a seven in the fourth against the United States (another 12-3 victory), the most points scored by either a men's or women's team in a single end.
However, vice-skip Anna Sloan, happy to see GB move into joint-third in the table - the top four progress to the semi-finals - played down the importance of records as they turn their attention to South Korea and Switzerland on Saturday.
She said: ''It (a record) builds momentum for the coming games and it's a good building block but unfortunately you don't get any prizes for getting them.
''But it's always good and it shows we are performing well and going in the right direction towards the end of the round-robin.
''It was great to beat the Japanese. It was a solid team performance and we supported each other really well."