Wales rallied to beat Japan 26-17 in the final Pool B game but must now settle for a shot at the Bowl trophy, where they will play Scotland in the quarter-final.
The Cook Islands and Tonga produced the performances of the day at the Fairmont Homes Adelaide Sevens to underline the strength of Pacific Island rugby and qualify for the Cup quarter finals along with the top seeds on an ultra-competitive day of rugby at the Adelaide Oval.
The Cook Islands let a 17-0 lead slip as they lost to Scotland early on but then beat Argentina 40-21 with a fine display of running rugby. The Cooks, Argentina and Scotland finished the day level on points but the Cooks' superior points difference took them through ahead of their rivals
The islanders join Series leaders New Zealand, defending Adelaide champions Fiji, Kenya, and South Africa, hosts Australia and Samoa, who came from behind against Tonga in the penultimate match of the day to win 14-12 and top Pool B and competition in the last eight for the Cup.
Cup Quarter-final draw
New Zealand v Tonga
Samoa v Cook Islands
South Africa v Kenya
Fiji v Australia