Wales were forced to overturn a half-time deficit as they battled to an unconvincing 22-18 victory over Japan in the first Test in Osaka on Saturday.
The visitors were oustcored two tries to one but a big second half saw them come from behind to snatch victory in the last quarter.
Wales hit the front for the first time on the hour mark having struggled at the breakdown and the set-pieces against a Japanese side seeking their first victory over a top-ten nation.
The hosts led 11-6 at the interval but couldn't match the strength of the Welsh bench as they faded in the latter stages of a hard-fought battle in temperatures in excess of 30 degrees at Hanazono Field.
Wales were without 15 senior players on duty with the British and Irish Lions in Australia, and a number of experienced names left out of the touring party, and it soon became apparent they would miss the presence of a genuine openside flanker.
Wales were on the back foot for much of the opening quarter and trailed 6-0 as Japanese full-back Ayumu Goromaru landed his first two shots at goal while Welsh number eight Rob McCusker was sent to the sin-bin.
Dan Biggar got Wales on the scoreboard as the visitors began to find some rhythm and the fly-half levelled the scores around the half-hour mark.
But it would be Japan who would cross the whitewash first as New Zealand-born flank Michael Broadhurst ghosted over on the stroke of half time after a line-out move.
Goromaru missed the conversion but Japan nevertheless went into the changing rooms with a five-point lead.
Japan still looked the better side after the interval, but Goromaru missed two penalty attempts.
Biggar landed two penalties in the second half to edge Wales ahead before wing Harry Robinson finished off a wonderfully-worked try — including a superb offload from full-back Liam Williams — to give the Six Nations champions some breathing room. Biggar converted.
But it would be a close finish as Japan came storming back. A series of drives up the middle eventually created space on the right for wing Yoshikazu Fujita to cross on the right.
Goromaru's conversion made it a one-point ball-game at 19-18 going into the final ten minutes.
But replacement fly-half Rhys Patchell would have the last laugh for Wales, slotting a 79th-minute penalty to secure the win.
The teams face each other again in Tokyo on Saturday, June 15.
The scorers:
For Japan:
Tries: Broadhurst, Fujita
Cons: Goromaru
Pens: Goromaru 2
For Wales:
Try: Robinson
Con: Biggar
Pens: Biggar 4, Patchell
Yellow card: McCusker
Japan: 15 Ayumu Goromaru, 14 Yoshikazu Fujita, 13 Male Sau, 12 Craig Wing, 11 Kenki Fukuoka, 10 Harumichi Tatekawa, 9 Fumiaki Tanaka, 8 Takashi Kikutani (c), 7 Michael Broadhurst, 6 Hendrik Tui, 5 Shoji Ito, 4 Hitoshi Ono, 3 Hiroshi Yamashita, 2 Shota Horie, 1 Masataka Mikami.
Replacements: 16 Takeshi Kizu, 17 Yusuke Nagae, 18 Kensuke Hatakeyama, 19 Toshizumi Kitagawa, 20 Ryuta Yasui, 21 Atsushi Hiwasa, 22 Yu Tamura, 23 Hirotoki Onozawa.
Wales: 15 Liam Williams, 14 Harry Robinson, 13 Owen Williams, 12 Jonathan Spratt, 11 Dafydd Howells, 10 Dan Biggar, 9 Lloyd Williams, 8 Rob McCusker, 7 James King, 6 Andrew Coombs, 5 Lou Reed, 4 Bradley Davies (c), 3 Scott Andrews, 2 Emyr Phillips, 1 Ryan Bevington.
Replacements: 16 Scott Baldwin, 17 Rhys Gill, 18 Rhodri Jones, 19 Andries Pretorius, 20 Dan Baker, 21 Tavis Knoyle, 22 Rhys Patchell, 23 Tom Prydie.
Venue: Hanazono Field, Osaka
Referee: Lourens van der Merwe (South Africa)
Assistant referees: Greg Garner (England), tba (Japan)
Assessor: Lyndon Bray
The win was an historic one for Samoa as it is the first time that they have beaten Scotland at Test level.
In the first game between these sides since the 2011 Rugby World Cup Final at the same venue, the All Blacks outscored their visitors two tries to one but were pushed all the way by a French side showing a marked improvement on their woeful Six Nations campaign.
The Sudamerica XV - representing the CONSUR nations - scored three tries of their own as England blew hot and cold.
Eight tries from the Lions including doubles from Mike Phillips and Alex Cuthbert set them on the road to success as encouraging moments were mixed with multiple handling errors — the Lions coming into their own to produce an excellent second half.
France battled to a 23-16 win over Scotland on a wet night in Paris in the final match of the 2013 Six Nations.
It was the perfect send-off for Italian prop Andrea Lo Cicero as the Azzurri finish the Championship in fourth, above the struggling Irish and French.
Two tries from Alex Cuthbert, who ends with four scores to his name, proved to be the turning point in the game after a first-half that ended try-less.
Six penalties from Toby Flood kept England ahead on the scoreboard as Italy recovered from a 15-3 deficit at the start of the second half to leave Twickenham on edge in a dramatic finish.
The Toulouse man's try six minutes from time, converted by Frederic Michalak, ensured the French ended their run of three straight defeats.
A match dominated more by the whistle and boot than any real memorable moments of attacking flair, Scotland and Wales racked up a total of 28 penalties between them as both sides continued to displease referee Craig Joubert.
It's the first time since 2001 that the Scots have won back-to-back Six Nations matches.
France were transformed from the sluggish side that were abysmal against Wales a fortnight ago — aggressive at the breakdown and benefiting from moving Wesley Fofana back into the centre after his ill-fated stint on the wing.
A severe downpour before kick-off hindered the handling ability of both sides through the first half, with Leigh Halfpenny adding three penalties for the visitors and Kristopher Burton responding with two for the hosts.
Stuart Lancaster's outfit put in another mature effort that leaves them as the last remaining unbeaten side in the 2013 Championship.
A solitary late try from wing George North handed Wales the spoils in a dour game that culminated to the sound of boos and whistles from the Parisian crowd.
Four tries, including a brilliant length of the field interception try from Stuart Hogg, led to a memorable victory for Scotland in front of a vocal home crowd at Murrayfield, compensating for the performance against England at Twickenham last weekend.
It was a sensational victory for the Azzurri who have now managed to beat Les Bleus twice in the last two years following their famous win in 2011.
The hosts enjoyed large portions of possession in both halves and arguably should have come away with more points, despite racking up four tries through Chris Ashton, debutant Billy Twelvetrees, Geoff Parling and Danny Care.