Yuka Tsuji vs Megumi Fujii was the superfight that everyone wanted but it never happened.
They both fought in the same organizations. And both were the biggest stars in Smackgirl and JEWELS. I think the organizations didn't want Fujii or Tsuji to lose. So they didn't make that fight.
Yuka Tsuji lost the first time to Anne Tavares, but Tsuji came into that fight with a heavily bandaged shoulder. Megumi then fought Tavares and won.
Another common opponent was Erica Montoya. Yuka Tsuji submitted Erica (btw, that was a good fight). Fujii won by decision.
I would say Fujii is #1 and Yuka was #2. MIKU was way overrated and never on the same level as Tsuji or Fujii.
I could only find the first round of Yuka Tsuji's fight with Erica Montoya. Like Fujii, most of Tsuji's matches very fairly short because they were so good at submissions.
Here is the first round of Erica Montoya vs Yuka Tsuji. This fight was in 2004. So this is well before WMMA even hit the US. It is one of the few fights that was actually very competitive. I think Erica was only 19 years at the time. A few months after losing to Tsuji, Erica fought Megumi Fujii, lost that fight, and then she stopped fighting MMA. If she was somehow still in fitting shape, Erica would probably submit a lot of today's WMMA fighters.