Fiji made a shaky start to the defence of their Olympic men’s rugby sevens title on Monday, almost undone by two Fijian exports in the Japan side in the opening round at Tokyo Stadium.

Tries by Fiji-born Lote Tuqiri and Kameli Soejima had given the host nation a 19-12 lead, with alarm bells ringing that an upset mirroring Japan’s stunning victory over New Zealand in the opening round of the Rio Games was on the cards.

But a late brace of tries by Waisea Nacuqu pushed Fiji back into the lead and an eventual 24-19 victory.

The Fijians did not wait long before bothering the scoresheet, Jiuta Wainiqolo crossing after just 20 seconds following a Japanese mistake from the kick-off.

Japan skipper Matsui Chihito responded in fine fashion, skipping away from a flat defence.

But Fiji again contested the restart, the ball finding Iosefo Baleiwairiki, who with one step was away to restore the lead.

Japan, however, held the half-time lead after Tuqiri was played into space after some clever footwork by New Zealand-born playmaker Colin Bourke.

An upset was on the cards as veteran Soejima soared to take the kick-off and fend off a lame challenge of a tackle by Jerry Tuwai for a try in the corner.

But Nacuqu pounced on two basic mistakes and Fijian worries were allayed.

Japan had one final chance when Asaeli Tuivuaka was yellow carded with 35 seconds to play, but a fluffed attacking line-out saw Fiji close down the game.

Britain, who won silver in Rio, beat Canada 24-0 with speedster Dan Norton – the top try scorer on the World Rugby Sevens Series – nabbing two tries.

South Africa, bronze medallists in 2016, saw off Ireland 33-14, with Sakoyisa Makata saying the team had overcome the absence of coach Neil Powell, in isolation after a Covid-19 outbreak.

“It didn’t really derail us,” Makata said, adding that Powell was now a “virtual” coach with his advice inputted live via laptop.

New Zealand, who failed to make the podium in Rio, crushed South Korea 50-5, skipper Tim Mikkelson dotting down twice to calm nerves after Jeong Yeon-sik had scored a memorable one for the Asian qualifiers in a competitive first-half.

Argentina raced out to a 24-0 half-time lead over Australia, but bruising ex-Wallaby centre Seru Kerevi scored one try and Josh Tuner two in a promising comeback before los Pumas saw the game out 29-19.

“We need to control the kick-off reception area. When we hold the ball, we attack really well, but Argentina put us under pressure and played a great game,” said the Fiji-born Kerevi, one of the few full 15s internationals at the Olympics.

The United States rounded out the opening morning’s play with a dramatic 19-14 victory over Kenya.

The two top teams from each pool plus the two best-placed third-placed teams advance to the Cup quarter-finals on Tuesday.