Olympic champions Britain began the women's hockey tournament with a stunning 2-1 loss against Germany on Sunday, while Australia defeated Spain in hot Tokyo conditions.
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After both sides took a knee before the opening whistle marked the start of the Britain-Germany match, the British women moved aggressively against their German opponents.
The first-quarter dominance led to an early lead for Britain after midfielder Sarah Jones netted the ball behind German goalie Julia Sonntag in the 13th minute.
Following an extended quarterly break due to the heat, Germany pulled level in the 24th minute after Viktoria Huse scored her 10th international goal through a penalty stroke.
"It's a nice feeling to start with a win especially against the gold medallist," Huse said.
"We know them quite well so it was a very tough game with us lucky at the end."
The young German team - average age 25 - kept fighting to have Charlotte Stapenhorst scoring the winning goal in the 33th minute shortly after the halftime break.
Britain's captain Hollie Pearne-Webb praised the team's positive start and dominance throughout much of the game, despite not taking a victory home.
"We all know that we're still in this," Pearne-Webb said.
"Game one is out of the way and it's a marathon, not a sprint."
Officials extended the breaks between quarters from the usual two minutes to four minutes to allow players to cope with the heat at the unshaded main pitch of the Oi Hockey Stadium.
The pitch was also sprayed with water during the longer halftime break to keep it fast and smooth.
In group B, Australia booked their first victory of the tournament, beating Spain 3-1.
The Hockeyroos were down 0-1 at halftime but turned the tide in the second half through field goals by Ambrosia Malone and Emily Chalker as well as a penalty corner by Grace Steward.