A penalty try and another by wing Akihito Yamada plus 16 points from the boot of fullback Ayumu Goromaru lifted Japan, who had only one win at seven previous tournaments, to second place in Pool B before leaders Scotland's clash with the Springboks in Newcastle.
Japan led 20-0 at halftime after Samoan indiscipline was punished with spells in the sin bin for forwards Faifili Levave and Sakaria Taulafo, during which Japan won a 23rd-minute penalty try.
Yamada beat his man to dive over in the corner on the stroke of halftime before Paul Perez ran in a consolation try for Samoa in the 65th minute at the end of a sweeping counter-attack launched from the islanders' own line.
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(Writing by Rex Gowar; Editing by David Goodman)
