The Japan international made the move to Brighton from Kawasaki Frontale in August 2021, but he spent the 2021-22 campaign on loan at Union SG before officially arriving at the Amex.
Mitoma was in impressive form for the Seagulls during the 2022-23 campaign, scoring 10 goals and registering eight assists in 41 appearances in all competitions.
The 26-year-old has also been an important player for Brighton this term, featuring on nine occasions, scoring three goals and registering three assists in the process.
Mitoma has entered the final two years of his contract at the Amex, and it does appear that Roberto De Zerbi's side will struggle to convince him to sign an extension due to the growing interest in his services.
According to Fichajes, both Man City and Man United are huge admirers of the forward, with the pair determined to secure his signature in 2024.
The report claims that the Manchester duo are planning offers when the January transfer window opens for business, but it will be difficult to convince Brighton to sell in the middle of the campaign.
Mitoma made his Europa League debut for the Seagulls last month against AEK Athens, while he has a record of 10 goals and nine assists in 40 Premier League appearances.
Man City brought in Jeremy Doku over the summer to boost their attacking options, but Riyad Mahrez departed, and it is believed that head coach Pep Guardiola wants to bring in another wide player next year, with Mitoma thought to be his leading target.
Man United, meanwhile, are also believed to be keen to sign a new winger during the winter window.
Antony is now back with the Red Devils after a leave of absence, but Jadon Sancho is still not involved in the first-team environment due to his falling-out with head coach Erik ten Hag.
Sancho is widely expected to leave the 20-time English champions on loan in January, with Borussia Dortmund thought to be interested in bringing him back to the club.
Man United have also been credited with an interest in Juventus' Federico Chiesa and Bayern Munich's Serge Gnabry at the start of 2024.
However, it has been reported that deals for either in the middle of the 2023-24 campaign are highly unlikely, which will seemingly force Ten Hag's side to switch their attention to other targets.