They overtook the British boat on the second upwind leg via a superior tack and superior speed for a 2:10 win to go three nil up in the first to five series.
The winners of the two semifinals will go head-to-head to decide who gets to challenge holders Oracle Team USA for the America's Cup itself, starting on June 17.
Percy, who was also sailing in Bermuda on Tuesday, was best friends with Simpson and won Olympic gold and silver medals with him in the Star class.
"The main emotion is an huge pride in what we have achieved in two years. we started with nothing", Barker told a televised news briefing. "Full credit to them". "We're going to be ready to go tomorrow".
In the second race, Team Japan had a bad gybe and buried its bows in the water just as the crew was crossing the boat.
"It's been a very up and down road for us, but it's nice to be hitting a bit of form now", Outteridge said.
"The racing yesterday was super tight and today was no exception as well".
"I'm so proud of the team and what they've achieved", he said.
June 9 Years after losing the 2013 America's Cup to Oracle Team USA, disappointment was still etched on Dean Barker's face.
Sir Ben Ainslie's hopes of delivering a first America's Cup title to a British team ended in semifinal defeat to New Zealand. "Boat is making its way back to dock to assess damage".
"It was unbelievable racing in gusts up to 27-28 knots".
The Japanese were swiftly up onto their foils and pulled clear of Artemis on the first leg.
Ainslie's Land Rover BAR crew pulled up on the third of seven legs after the camber arm in the high-tech wing sail broke.
"It's been a fantastic honour and a privilege to be running a new team. and I would not trade that for anything". "It's been nice to have Japan back in the America's Cup", Barker said, declining to commit his own future.
"There are probably a few tweaks we can make to make it more compatible across a wider wind range, and I know the teams are looking at that".
We had our heads down making sure we were getting everything out of our boat we could to make sure we got past and then realised they had slowed down, and didnt really realise why until we sailed past them about a minute or so later..