He scored his 11th try in six appearances during the Hino Red Dolphins' 41-26 loss to the Urayasu D-Rocks.
While Israel Folau was a late withdrawal on Saturday after having been named to play, the second division leaders still fielded an imposing combination which included former Scotland international Greig Laidlaw.
Ex-Wallaby flanker Liam Gill also featured for D-Rocks, enjoying a mixed day which included both a try and a yellow card.
Yet despite their heavyweight line-up, the D-Rocks still couldn't contain the former Melbourne Storm age-grade representative, whose fifth try of the season helped to close Hino to within eight points before the unbeaten Urayasu dominated the final 20 minutes.
Born in southern New Zealand, before spending part of his upbringing on the remote Chatham Islands, 800km east of Christchurch, Peni played for the Western Force and Brumbies before making his way to Japan.
The 29-year-old scored nine tries in seven appearances last season, finishing with hat-tricks in each of the last two games, and then started 2023 the same way, with the third treble of his JRLO career.
Saturday's try was Peni's 14th from 11 games, representing a great piece of transfer business by his club.
It is a strike-rate even Folau, who has scored 15 from 17 games since moving to Japan, can't match.
D-Rocks are the only unbeaten side left in Division Two, while Marika Koroibete's Saitama Panasonic Wild Knights, and Bernard Foley's Kubota Spears Funabashi Tokyo-Bay, remain undefeated in the top section.
Koroibete scored his third try of the season to help Saitama overpower the Ricoh Black Rams 38-17, while Foley kicked 10 points as the Spears narrowly held off Kobe 25-21.
Wallabies halfback Nick Phipps and his Springboks counterpart Faf de Klerk were both try-scorers as Yokohama Canon Eagles beat the NEC Green Rockets 36-12.
The game also saw Canon's Tongan-born Japanese representative Amanaki Lelei Mafi, who played two seasons for the Melbourne Rebels in 2017 and 2018, score a first-half hat-trick.
Phipps scored the second of the Green Rockets' tries, but Michael Cheika's side were held scoreless after halftime for the second week in a row.
Will Genia's Hanazono Kintetsu Liners, who had conceded 151 points in the previous two weeks, put up more of a fight against Tokyo Suntory Sungoliath before falling away in the second half to lose 51-10.
Sunday's other matches in the top division were officiated by Australian referees at the invitation of the Japanese Rugby Union, with Nic Berry taking the whistle as Toshiba Brave Lupus Tokyo thumped Toyota Verblitz 63-25, while Angus Gardiner oversaw the Mitsubishi Heavy Industries Sagamihara Dynaboars' 27-all draw with the Shizuoka Blue Revs.
Elsewhere in Division Two, Wallabies fullback Tom Banks's Mie Honda Heat scored two tries in the last seven minutes to beat bottom side Shimizu Corporation Koto Blue Sharks 29-10.
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