The temperature was still hovering above 37C at the 4.30pm (AWST) kick-off on Friday, but the first half was still a fast and entertaining affair that featured five tries.
Force hooker Sara Cline opened the scoring with a third-minute try, but the Phoenix hit back with two in the space of five minutes.
Scores were level again at 14-14 in the 20th minute when Force fullback Aiysha Wigley danced through Tokyo's defence to touch down.
Aiysha Wigley crosses for a Force try during their trial loss to Tokyo Sankyu Phoenix. (Richard Wainwright/AAP PHOTOS)
A yellow card to Force five-eighth Nicole Ledington in the 37th minute left the home side vulnerable, with Tokyo winger Yuina Yamamoto crossing less than a minute later to give the visitors a 19-14 lead at the break.
Force coach Dylan Parsons made plenty of changes in the second half in a bid to give his entire squad minutes.
Powerful Force lock Michaela Leonard almost levelled the scores in the 52nd minute, but her try was rubbed out on review due to a knock-on.
The Force controlled large parts of the game from that point on, but were let down by more handling errors when in attacking positions.
In contrast, Tokyo were clinical when given a sniff, with Suzuha Okamoto crossing for her second try in the 68th minute to give her team a match-winning lead.
The Force's pre-season campaign continues with a scrimmage against Tokyo at UWA Sports Park on Tuesday, before taking on the Melbourne Rebels on March 2.