Manchester United and Manchester City both are rumoured to be planning to sign Brighton winger Mitoma in January. I would like to see Manchester United signing him instead because they would make use of a productive player like him more now. They are in a really desperate condition now.
Brighton wants to extend his contract. Undoubtedly, Mitoma will want to leave Brighton if Manchester teams are interested in him, but it is hard to predict which team he will choose. There is a very high level of competition at Manchester City. He will have to compete with star players like Phil Foden and Jack Grealish, but I think he has a slightly better chance of being in the starting 11 at Manchester United. No doubt it will be a difficult decision for him if this transfer happens.
Mitoma is an important palyer in Brighton and his effect on Brighton is the reason to say Brighton won't lose this player easily.
However, Manchester United is not in a good situation and there is a lower chance for Mitoma to accept this offer if Pep Guardiola sends him an offer at the same time. The contract with Mitoma will expire in 2025 and if he continues his good performance he can even be linked to other teams.