Dimos (or Marigno, depending on the source) is a defender wearing #3. He's modeled after the real Italian player Giampiero Marini. Not much is known about him beyond that—his full name hasn't been confirmed anywhere.
The confusion around his identity comes down to how he appears across different Captain Tsubasa media. Teammates call him Dimos in the manga itself, but the 3109 Perfect Data lists him as Marigno instead. It's possible these are actually two different players, which would explain the name discrepancy, especially when looking at how Captain Tsubasa J: Get In The Tomorrow handles the roster.
Content compiled by AnimeList.moe from publicly available sources.
