Ji Dong-Won joins Augsburg
The South Korean has found first-team opportunities limited at the Stadium of Light this season, making just two Premier League starts.
Having struggled to make an impact since arriving on Wearside from Chunnam Dragons in 2011, the 22-year-old scored five goals in 18 appearances in all competitions on loan at Augsburg last season.
And both clubs have now confirmed the deal which sees Ji return to Germany.
"We have now taken the opportunity to take Ji Dong-Won for the rest of the season under contract," Augsburg sporting director Stefan Reuter said.
"Because he had a successful time at the Augsburg last season, he knows the team, the coaching staff and the environment.
"For him there is no settling time and we have therefore decided to transfer for this limited period."