Italy remained winless in 2014 after crashing to a third loss in June with a 26-23 defeat against Japan in Tokyo on Saturday.
The result is the Brave Blossom's first-ever victory over Italy as the Azzurri slumped to their ninth consecutive defeat.
The scores were level at 13-13 at half time but New Zealand-born Male Sa'u ran in a try midway through the second half to lead Japan to their tenth straight Test-match win.
Sa'u's converted try gave Japan a 26-16 lead at the Prince Chichibu memorial ground.
Robert Barbieri crossed for Italy late on to cut the deficit to three but the visitors ran out of time.
Ayumu Goromaru accounted for 14 points for Japan with four penalties and a conversion.
Saturday's encounter was Japan's only game against a Six Nations side before the 2015 Rugby World Cup where Japan will compete in Pool B against South Africa, Scotland, the United States and Samoa.
More to follow...
Tries: Yamada, Sa'u
Cons: Goromaru 2
Pens: Goromaru 4
Yellow Card: Yamada
Tries: Penalty Try, Barbieri
Cons: Orquera, Allan
Pens: Orquera 2
Japan: 15 Ayumu Goromaru, 14 Akihito Yamada, 13 Male Sa'u, 12 Yu Tamura, 11 Kenki Fukuoka, 10 Harumichi Tatekawa, 9 Fumiaki Tanaka, 8 Ryu Koliniasi Holani, 7 Michael Leitch, 6 Justin Ives, 5 Luke Thompson, 4 Shoji Ito, 3 Kensuke Hatakeyama, 2 Shota Horie, 1 Masataka Mikami.
Replacements: 16 Hisateru Hirashima, 17 Takeshi Kizu, 18 Hiroshi Yamashita, 19 Shinya Makabe, 20 Hitoshi Ono, 21 Hendrik Tui, 22 Atsushi Hiwasa, 23 Toshiaki Hirosi.
Italy: 15 Luke McLean, 14 Leonardo Sarto, 13 Michele Campagnaro, 12 Andrea Masi, 11 Giovambattista Venditti, 10 Luciano Orquera, 9 Tito Tebaldi, 8 Robert Barbieri, 7 Mauro Bergamasco, 6 Joshua Furno, 5 Marco Bortolami, 4 Quintin Geldenhuys (c), 3 Lorenzo Cittadini, 2 Leonardo Ghiraldini, 1 Alberto De Marchi.
Referee: Jaco Peyper (South Africa)
Assistant referees: Garratt Williamson (New Zealand), Brendon Pickerill (New Zealand)
TMO: Peter Marshall (Australia)