Fiorentina send Savio to Bulgaria
Ugandan-born Nsereko, 21, who helped Germany win the 2008 European Under-19 championship, joined Fiorentina from West Ham United in 2009.
"I'm very pleased to be here," Nsereko told reporters. "This is not a step backwards in my career and you'll see that I was right to join Chernomorets at the end of the season."
Chernomorets are third in the standings with 28 points, nine points behind leaders Litex Lovech in the mid-season break.