[Entity Framework] Issues with .Include()

public class Set
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public string Code { get; set; }
        public DateTime? ReleaseDate { get; set; }
        public string Type { get; set; }
        public string? Series { get; set; }
        public string? Description { get; set; }

        public ICollection<SetContent> Content { get; set; }
    }

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public class SetContent
    {
        public int Id { get; set; }
        public int SetId { get; set; }
        public string? SetCode { get; set; }
        public string? SetRarity { get; set; }
        public string? SetRarityCode { get; set; }
        public int ItemId { get; set; }

        public virtual Item Item { get; set; }
    }

--------------------------

public class Item
    {
        public int Id { get; set; }
        public string Name { get; set; }
        public string Type { get; set; }
        public string Desc { get; set; }
        public string ImageBig { get; set; }
        public string ImageSmall { get; set; }

        public List<SetContent> Sets { get; set; } = new List<SetContent>();
    }

{
  "id": 0,
  "name": "string",
  "type": "string",
  "desc": "string",
  "imageBig": "string",
  "imageSmall": "string",
  "sets": [
    {
      "id": 0,
      "setId": 0,
      "setCode": "string",
      "setRarity": "string",
      "setRarityCode": "string",

      "Name": "string",
      "ReleaseDate": "DateTime"
    }
  ]
}