The goal was the 24-year-old Brazilian's first in a Crew shirt after his transfer from Brazilian side Ceara SC was sealed in January. It preserved Columbus' unbeaten record (2-0-3) this preseason.
Opoku contributed the setup only minutes after his entrance late in the first half.
Former Orlando City U-23 player Ian Svantesson scored early on a corner kick header for Charleston.
- 25' - CHL - Ian Svantesson (Nico Rittmeyer)
- 45'+ - CLB - Robinho (Edward Opoku)
Charleston: Kuzminsky, Woodbine (Nelson 45'), Bolt (Amoo 67'), Archer, van Schaik, Anunga (Mason 62'), Kelly (Daley 83'), Candela (Etim 77'), Rittmeyer (Marini 45'), Piggott (Higashi 72'), Svantesson (Bosua 59')
Columbus: Jon Kempin, Lalas Abubakar, Aboubacar Keita, Josh Williams (Alex Crognale 31'), Connor Maloney, Ricardo Clark (Aidan Morris 85'), Niko Hansen (Edward Opoku 39'), Eduardo Sosa (Berhalter 46'), Robinho, Luis Argudo, Patrick Mullins (JJ Williams 62')