The No.3-seeded Errani was the first to go, falling behind 3-0 in each set and, after catching up to 3-all both times, just getting pipped at the end of the set to fall to Kuznetsova in straight sets, 64 64.
Though it was an upset on paper - Errani is ranked No.6, Kuznetsova No.27 - it wasn't really that big a surprise given Kuznetsova had won five of their six previous meetings (now 6-1 in their head-to-head).
The No.9-seeded Stephens followed Errani to the sidelines, dropping a dramatic three-setter to Bouchard, 57 76(7) 63. Stephens pulled off a miracle comeback early in the match, falling behind 5-0 but then winning seven straight games to take the first set; she eventually found herself just two points away from winning the match leading 75 53, but Bouchard never stopped fighting, winning in three.
"It was definitely an up and down match," Bouchard said. "I've known her since I was 12, and I've practiced with her a lot, so it's always tough playing someone like that - it's always a bit more mental.
"I was disappointed with that first set, but she definitely raised her level. But then I kept trying and fighting, and even when my level wasn't quite there, I stayed positive. I think that paid off today."
Besides her great results so far this week, there's another reason that Bouchard is enjoying herself in Tokyo - the Canadian was asked in her post-match press conference about her affinity for Hello Kitty.
"Does everybody know about this!" she replied. "Oh my God. Well, yes, I am obsessed, it's true. I went to Asia for the first time last year, so this is my second time playing in Tokyo, and every time I come here I go to the Hello Kitty stores. And the fans are so nice here too, they give me a lot of gifts."
The other seeds in action early on all won, with No.6 seed Jelena Jankovic firing seven aces during a 64 61 win over Ayumi Morita; No.11 seed Ana Ivanovic winning nine straight games to close out Elina Svitolina, 63 60; No.12 seed Sam Stosur battling back from 5-3 down in the second set to beat Kimiko Date-Krumm in straight sets, 63 76(2); No.15 seed Sorana Cirstea beating Misaki Doi, 61 62; and No.16 seed Dominika Cibulkova beating Australian qualifier Casey Dellacqua, 75 63.
"It was a lot harder than the score indicates," Ivanovic said about her match. "The conditions were tough out there - it was gusty, and on one side it was a lot harder to control the ball, but I'm very happy I managed to settle down and after the first set things got much, much better for me out there.
"I always enjoy coming back to Tokyo. This is the eighth time I've played this tournament and I always love seeing the fans - they are very passionate about tennis, which is obviously really nice to see."