Berlin - South Korea's Koo Ja-Cheol says his move from Mainz back to Bundesliga rivals Augsburg "feels like coming home" after signing a two-year deal with the Europa League side.
The 26-year-old winger joined Mainz in January 2014, after spending the 2012/13 season on loan at Augsburg from Wolfsburg and has now returned to the Bavarian team.
"I've always felt comfortable at Augsburg and now have the feeling of coming home," said Koo, who passed the medical on Monday before the transfer window closed.
"It's great that it worked out at such short notice.
"Now I am looking forward to being back at the club and I want to help the team achieve their goals in the Bundesliga, cup and Europa League."
After signing his Augsburg contract on Tuesday, Koo, who captained Korea at the 2014 World Cup, flew off to link up with the squad for their Russia 2018 qualifiers at home to Laos on Thursday and away to Lebanon next Tuesday.
His new club said they were delighted to have Koo back after the Korean scored eight goals in 36 league games for Augsburg.
"We were in regular contact with Koo Ja-Cheol after his departure and we took the chance to have him back as soon as it emerged," said Augsburg's director of sport Stefan Reuter.
"He knows the club, the environment as well as the team and coach, so he won't need much time to settle back in here.
"From a sporting perspective, he will help us in attack to get more width on our game."