Following a series of reports about a move away, the 19-year-old signed a five-year extension earlier this week to put to rest the exit speculations.
Giants AC Milan had been linked to the full-back.
''Five years contract is a clear attestation that Sassuolo strongly believe in me," Adjapong said.
"I just extended my contract to another five years and I'm very glad that the club has a trust in me to offer me the new deal.
''I'm proud to be part of a club that believes in youngsters like me.
''I never concentrate on any stiff competition for a playing role as I'm equally motivated to give my best for the club.
''Although, expectations are high, that should serve as an extra motivation and not a burden."
In only his first campaign of professional football, the right-back made nine league appearances, scoring in the 4-3 defeat to Cagliari.
He also featured three times in the Europa League.
Born to Ghanaian parents in Italy, the youngster has featured for the Europeans at youth level.
That said, he still remains eligible to play for the Black Stars as he is yet to make a competitive senior appearance for Gli Azzurri.