Sai Nanami

Sai from a very young age showed a great ability to perform mathematical exercises of great difficulty without any problem, so because of that his father and guardians expected a lot from him, increasing the load on his homework and exerting too much pressure, so Sai began to show all rejection to the fact that they considered him a mathematical genius, reacting negatively when someone mentioned it. The relationship with his brother Ryusui was not the best in his childhood either, since the extroverted, arrogant and greedy personality of his brother contrasted greatly with his, especially when Ryusui asked Sai to help him calculate formulas or teach him chess since his brother "wanted" his mathematical ability to achieve things he wanted, as a result, every time Ryusui appeared Sai escaped so as not to have to do it. Despite everything, he is a very passionate boy with what he really likes since he dreams of being a game programmer, demonstrating a very professional attitude when we see him manually writing the code to create Dragon Quest. He can also be seen to be a little shy around the girls, appearing somewhat embarrassed when geographer Chelsey speaks to him and asks him to accompany them and join the realm of science.

Sai is a youthful-looking and handsome young man, whom Chrome describes as "a handsome genius." He is of similar build and height to his brother, with black or brown hair that sweeps to one side, partially covering his face with wavy ends. He has prominent eyebrows, and like other de-petrified individuals, he bears a petrification mark that completely covers both hands. Since his de-petrification, he has worn a shirt similar to Senku's and black pants adorned with a belt featuring a cross and a "C" (referencing the C++ programming language). He completes his outfit with elegant black dress shoes.

At just four years old, he could multiply ten-digit numbers. Because of his abilities, he was kept working all day, even though he really just wanted to program. Fed up with his brother, he went to a university in India, where he taught classes to earn money.