You could start by checking major online retailers that specialize in manga. They might have the Portuguese version of Hitorijime My Hero. Social media groups dedicated to manga could also provide leads. Additionally, you can reach out to comic book conventions or events, as they sometimes have vendors selling such rare editions.
The similarities are that the key events and character developments are maintained. However, the anime might add or cut some minor details for better visual presentation. Also, the voice acting and soundtrack in the anime give it a unique feel compared to the manga.
My Hero Academy Manga is a Japanese manga produced by Xiongying Society. It tells the story of a group of students who became heroes through hard work. The work was widely welcomed in Japan and around the world, with many loyal fans.