The result means that, with Kyle Smith's men winning their Page Play-off earlier, both Scottish teams will play for gold in today's finals at the World Junior Curling Championships in Sochi, Russia.
Fleming is defending the world title she won last year, when Smith took bronze, and this is the first time since 1996 that Scottish teams have reached the men's and women's finals, with the last time Scotland achieved a golden double being in 1993.
After last night's semi-finals, both Scottish teams will face Russia in their finals, with the Russian women beating Japan 8-6 in their semi-final, and the Russian men completing an 11-8 extra-end win over Canada.
After her win, Fleming said: "Japan played outstandingly. Of all the teams we've played this week, they've definitely asked us the most questions. We just managed to keep with them the whole way."