The 19-year-old winger joined the club in 2015 but is yet to appear for the first team. He did though appeared on the bench four times last season.
He has impressed with their other teams though, scoring 8 goals in 19 appearances for the under-23 side in the Regionalliga West last season.
Sporting director Uwe Klein said the Japanese-born Appelkamp “has undergone great development in our academy,” and he describes him as “an enormously willing and capable player,” whom the club see “a lot of potential in the future.”
“The club’s trust in me makes me very proud,” said Appelkamp. “I will do my utmost in training every day so that I can continue to develop.”
The club have yet to announce any new signings but Appelkamp will be joined in the first team squad by 18-year-olds Dennis-Adam Gorka and Nikell Touglo. Adam Bodzek has also signed a new deal with the side.