Napoli confirmed on Saturday that they had signed Giacomo Raspadori from Sassuolo, the third transfer completed by the Serie A club in as many days.
In a statement Napoli said that they had brought in the 22-year-old Italy international "on loan with an obligation to buy", effectively making it a permanent transfer to southern Italy's biggest club.
Napoli did not reveal the details of the deal.
However, according to widespread reports in Italian media, the two clubs agreed to a five million euro loan plus a further €25 million to be paid over three years after the move is officially made permanent next summer.
Forward Raspadori has played 13 times and scored three goals for Italy, featuring in the squad which won Euro 2020 last year.
His arrival is one of three deals this week which have helped reignite enthusiasm around Napoli after a troubled summer marked by fan anger and the departures of supporter favourites Kalidou Koulibaly, Lorenzo Insigne and Dries Mertens.
Giovanni Simeone completed his move on loan from Verona on Thursday before France midfielder Tanguy Ndombele arrived from Tottenham Hotspur, also on loan.
Napoli, who host promoted Monza on Sunday, are also tipped to bring in goalkeeper Keylor Navas from Paris Saint-Germain.