World number 12 Takeda and 139th-ranked Okayama struck matching 67s on the Welsh coast as compatriot Miyu Yamashita finished a single shot adrift.
A large group of players were at three under par on a congested leaderboard in the final major of the year.
Takeda bounced back strongly from a double-bogey seven at the ninth with four birdies down the stretch, while Okayama opened with a bogey five before sinking six birdies.
Defending champion Lydia Ko finished one over, while world number one Nelly Korda is three off the lead after a two-under 70, finishing with a birdie after nine straight pars.
"I had a double bogey today, but I was able to quickly change my mindset, and it was good that I was able to do that," said Takeda.
"Other than that, I was able to save par and make some birdie putts, so I played very consistently."
Australia's Minjee Lee, who won the Women's PGA Championship last month, also finished with a 70.
Fellow Australian Grace Kim, who triumphed at the recent Evian Championship, is one under par.
Pre-tournament favourite Lottie Woad, playing at her first major as a professional, ended her round on level par, upstaged by English compatriot Mimi Rhodes, who finished her round two off the lead.
"It's one of those rounds that could have got away from me so I am happy I hung in there," said Woad, fresh from winning the Women's Scottish Open last week.