The talented youngster, who is only 15, has been secured by Newcastle United.
The Magpies, per Chronicle Live, have beaten out several top clubs for his signature.
The likes of Chelsea and Fulham were circling to sign Kouossu, who has been a revelation in the West Brom academy.
The teenager posted a message on his Instagram account this week that stated: "Never thought this day would come but I announce with a heavy heart after 8 years at the club that I have officially left West Brom
"I would like to give a huge thank you to all the coaches and staff for pushing me to my limits year after year and all of the outstanding team-mates throughout the years on the pitch.
“But I believe this decision was necessary and the story must continue, thank you Baggies."