Newcastle signed Japan forward Yoshinori Muto from Mainz on a four-year contract on Thursday, hours after manager Rafa Benitez hinted at concerns over a lack of transfer spending following a 4-0 friendly defeat.
Newcastle said last week that they had reached an agreement with the Bundesliga club for the transfer. Muto's move was completed on Thursday after he was granted a work permit.
Muto, 26, has played 25 times for Japan and featured in one game at the recent World Cup, the 1-0 loss to Poland. Reports said Muto's transfer fee was around £9.5 million.
"I'm honoured to be a player for such a big club," said Muto, the first Japanese player to join Newcastle.