The 26-year-old joined the Seagulls from Japanese club Kawasaki Frontale in August 2021 and was then sent out on loan to Union SG for the 2021-22 season before establishing himself as a star player on the South Coast under the tutelage of head coach Roberto De Zerbi.
Mitoma contributed with 10 goals and eight assists in 41 appearances for Brighton across all tournaments last season, helping the Seagulls finish sixth in the Premier League and qualify for the Europa League for the first time in their history.
The Japan international has since impressed at the start of the new campaign, scoring three goals and registering four assists in 10 games across all competitions, including an assist in Brighton's 2-2 draw with Marseille in the Europa League on Thursday.
Mitoma's rapid rise on the European stage is understood to have caught the eye of a number of top clubs, with a recent report claiming that both Man City and Man United are weighing up a January move for the winger.
The likes of Arsenal, Chelsea, Liverpool, Real Madrid, Barcelona and Bayern Munich have also been credited with an interest in Mitoma, who has entered the final two years of his contract at the American Express Community Stadium.
However, according to LondonWorld, Mitoma has turned down advances from clubs across Europe and is set to commit his future to Brighton by signing a new five-year contract, which would keep him tied to the club until the summer of 2028.
The report adds that the winger has agreed terms over a new £80,000-a-week contract, and the deal is expected to be finalised within the next 24 hours.
Lead agent Keisuke Sekine is said to have been a key figure behind the scenes in negotiating the deal, with Mitoma fully committed to the project at Brighton under De Zerbi.
Mitoma's proposed new deal comes as blow to clubs such as Man United, who are believed to be in the market for a new winger of the Japanese's calibre.
Antony has recently been reintegrated into Erik the Hag's first-team squad, but Jadon Sancho is reportedly likely to leave the club in January due to his well-documented stand-off with the Red Devils manager.
Man United have also been linked with another Brighton star in the form of Evan Ferguson, with a report last month claiming that the Red Devils failed with a £50m offer for the hightly-rated 18-year-old striker during the summer transfer window.
Nevertheless, Ferguson allegedly turned down the chance to make a summer switch to Old Trafford in favour of remaining at Brighton, where he has scored 18 goals in 39 senior appearances since making his debut in August 2021.