The anime where the male lead becomes small

Answer 1

There were many classic examples of animes where the male lead became smaller:
1. Alan from The Attacking Giant. In the story, Allen had once become a miniature version of Mikasa due to the attack of a giant. He had experienced many difficult adventures and growth.
2. Kimki Ken from Tokyo Ghoul. In the story, Kim Muyan became a ghoul because of the infection. Later, for some reason, he shrunk to the size of a primary school student and continued to fight with his companions.
3. Naruto Uzumaki from Naruto. In the story, Naruto was sealed in Payne's trap when he was a child and later transformed into a ninja, eventually becoming a great ninja.
These examples are very popular. You can choose one or more of them as a reference according to your preferences.