Here, the PA news agency wraps up Sunday's action and takes a look at Monday's fixture where Wales take on Georgia.
Five points on the board for England
England got their tournament under way with a bonus-point win but a less-than sparkling display as they beat Tonga 35-3 in Sapporo.
Manu Tuilagi was the stand-out performer, scoring two tries in the first half that were added to by efforts from Jamie George and, late on, Luke Cowan-Dickie, while skipper Owen Farrell contributed three penalties and three conversions.
Notable handling errors were made, and boss Eddie Jones afterwards told ITV his side had not been sharp enough, while also claiming it was "a bit like playing against Stoke City – the ball went out a lot, there was a slow pace to the game".
He added: "Maybe that was the intention. You just have to battle that, get on with it, and you only have to get four tries in 80 minutes and we got them."
England's next match is against the United States on Thursday.
Ireland triumph in Home Nations battle
Joe Schmidt's Ireland, who entered the tournament as the world's top-ranked team, emerged from their Pool A clash against Scotland victorious and with a bonus point, winning 27-3 in Yokohama.
James Ryan, Rory Best and Tadhg Furlong all scored tries in the first half before Andrew Conway crossed for Ireland's fourth.
Adding to Scotland's woes was an injury to Hamish Watson that could mean his World Cup is over, with boss Gregor Townsend saying it "doesn't look good" for the flanker.
The team that finishes second in this group will have a quarter-final match against the winner of Pool B – which is expected to be reigning champions New Zealand. Ireland next face hosts Japan on Saturday, with Scotland taking on Samoa two days later.
Italy clinch five points as well
Italy bounced back from a slow start to also open their campaign with a bonus-point win, seeing off Namibia – who at 23 are ranked lower than any other side in the tournament – 47-22 in Pool B.
The Azzurri fell behind early on in Higashiosaka via Damian Stevens' try, before going on to register seven of their own, including a penalty try. Tommaso Allan scored one of them and also added three conversions.
Italy boss Conor O'Shea afterwards said his side's performance "wasn't very pretty" and vowed there will be a significant improvement come Thursday's clash with Canada, while counterpart Phil Davies expressed his pride in his players after their three-try showing.
Conway secured the bonus point for Ireland with a smart finish in the 56th minute as he took the ball from Conor Murray and raced in at the right corner.
Italy captain Sergio Parisse has now appeared at five Rugby World Cups and the 36-year-old back row is only the third player to do, the others being his former team-mate Mauro Bergamasco and Samoa's Brian Lima.
Wales v Georgia (Pool D, Toyota)
Warren Gatland's Wales get their campaign started after a build-up disrupted by assistant coach Rob Howley being sent home over an alleged breach of World Rugby's betting regulations, with Stephen Jones replacing him.
Boss Gatland has stressed the need for focus on the task ahead, saying: "It's been tough, but you have to draw a line in the sand and concentrate on what your job and your role is."
The reigning Six Nations champions, occupiers of World Rugby's number one ranking position last month, began the World Cup ranked fifth, seven places above Georgia, who they beat 13-6 in 2017.
Gatland is stepping down as head coach after this tournament. In the New Zealander's 12-year reign, Wales have won four Six Nations titles and three Grand Slams, and reached the 2011 World Cup semi-finals.