Argentina claimed their first win of their World Cup Pool C campaign with a bonus-point victory over Tonga.
The Pumas started brightly as Julian Montoya scored the opening two tries with Santiago Carreras adding a third.
Hooker Montoya completed his hat-trick to secure the bonus-point in the 25th minute before Telusa Veainu scored Tonga's first try of the tournament.
Veainu crossed again after a neat backs move following the break but the Pumas remained resolute in Higashiosaka.
The South American side were not at their best but they seized on Tongan mistakes to all but seal victory in the first half, as they prepared for their next match with England in clinical fashion.
The Polynesian kingdom will be encouraged by their spirited response after the interval, scoring the only try of the half when full-back Veainu dived in the corner after a delicate offload by Cooper Vuna.
The results sees the Pumas move into second in Pool C, four points behind England, who they face in Tokyo on Saturday, 5 October (09:00 BST).
Tonga are in next in action against France on 6 October (08:45).
Teams
Argentina: Boffelli; Moroni, Orlando, de la Fuente, Carreras; Urdapilleta, Cubelli; Tetaz Chaparro, Montoya, Figallo, Petti, Lavanini, Matera, Kremer, Lezana.
Replacements: Creevy, Vivas, Medrano, Alemanno, Ortega Desio, Ezcurra, Sanchez, Delguy.
Tonga: Veainu; Lolohea, Hingano, Piutau, Halaifonua; Faiva, Takulua; Fisiihoi, Ngauamo, Tameifuna, Lousi, L. Fifita, Kalamafoni, Kapeli, Vaipulu.
Replacements: Sakalia, V. Fifita, Fia, Mafi, Manu, Fukofuka, Fosita, Vuna.