How can I get the values of a model class by Id and together, the values of another internal class?

I have the class Digit and it has a many-to-many relationship with the User class.

How can I search for users related to a search by the digit ID?

 @Entity
 public class Digit implements Serializable {

     private static final long serialVersionUID = 1L;

     @Id
     @GeneratedValue(strategy = GenerationType.IDENTITY)
     private Integer id;

     // ...

     @JsonIgnore
     @ManyToMany(mappedBy = "rDigit")
     private Set <User> user = new HashSet<>();

     // getters and setters
 }

My service:

public Digit findDigitById(Integer id) {
    Optional<Digit> obj = digitRepository.findById(id); // This search does not bring the user
    if (obj.get() == null) {
        throw new ObjetoNaoEncontradoException("Some error: " + id);
    }

    return obj.get();
}

User class:

@Entity
public class User implements Serializable {

.....
@Id
@GeneratedValue(strategy = GenerationType.IDENTITY)
private Integer id;

    @JsonIgnore
    @ManyToMany
    @JoinTable(name = "USER_DIGIT", joinColumns = @JoinColumn(name = "user_id"), inverseJoinColumns = @JoinColumn(name = "digit_id"))
    private Set<DigitoUnico> rDigit = new HashSet<>();

... getters and setters...
}