Parsons' score was her 25th international try, extending her Irish record as Ireland finished strongly to seal a comfortable win.
Ireland have beaten Japan 43-19 in Cork to secure a second victory over the visitors in the space of a week.
Scott Bemand's side scored seven tries at Virgin Media Park, with Béibhinn Parsons, Brittany Hogan, Neve Jones, Eilís Cahill, and Anna McGann all crossing.
There were also debut tries for Alana McInerney and Sophie Barret, helping Ireland pull clear after Japan threatened a second-half comeback.
Parsons' score was her 25th international try, extending her Irish record as Ireland finished strongly to seal a comfortable win.

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