He first appeared in Captain Tsubasa ch. 51 "Opening Ceremony".

He's the private Language teacher of Tsubasa Ozora, who helped him during his last year of middle school in order to get prepared for his departure to Brazil. He usually appears in the Ozora household and also cheered his student in the finals of the middle school tournament.

Carlos is very cheerful but also determined to make Tsubasa a good learner, always teasing his student that he gives more importance to Football (even stopping lessons abruptly) than his Portuguese studies.

The second season of Captain Tsubasa (2018).
 
The International Junior Youth Tournament in Paris, France, is about to begin, and Tsubasa, Misaki, Wakabayashi, Hyuga, and Wakashimazu are ready. Japan’s team of elite players is to face off against the best the soccer world has to offer. Germany’s Schneider, France’s Pierre, Argentina’s Diaz, and Italy’s Hernandez await, along with a host of other new rivals. Let the battle begin! 
(Source: VIZ Media)