Inter Milan will reportedly receive €7.5 million plus a 10 per cent sell-on clause from any future transfer.
There is no buy-back clause in the deal, with Inter letting go of their youth academy product.
There had also been interest in Akinsamiro this summer from the likes of Bologna, Werder Bremen and Borussia Mönchengladbach.
The Nerazzurri signed Akinsamiro from Nigeria Premier Football League (NPFL) outfit Remo Stars in January 2023.
The 21-year-old made one league appearance for Inter Milan, winning the Serie A title with the Black and Blue in the 2023/24 season.
Akinsamiro spent the following season on loan at Sampdoria, scoring once in 35 league appearances.
The defensive midfielder was sent on loan to Pisa last season, where he registered one assist in 25 league appearances.