Sai Nanami.

Sai Nanami is a calm, logical person who struggles a bit with social situations. She tends to take everything literally and gets easily frustrated when things don't go as planned. Even so, she is obedient, curious, and very expressive when she panics or is surprised. Sai Nanami is usually more notable for her expression and nervous/logical demeanor than for a striking appearance. Her design is quite simple to highlight her analytical personality and her role within the science group.

Senku Ishigami: The protagonist. He is a scientific genius who wants to rebuild civilization using scientific knowledge.
Taiju Oki: Senku's best friend. He has enormous physical strength and great stamina, although he is not known for his intelligence.
Yuzuriha Ogawa: A friend of Senku and Taiju. She is very skilled at crafts and helps make clothes and repair objects.
Gen Asagiri: A highly intelligent mentalist who uses psychology and persuasion to help the Kingdom of Science.
Ryusui Nanami: An excellent navigator and entrepreneur. His dream is to explore the world and achieve everything he desires, always helping the Kingdom of Science.
Sai Nanami: Ryusui's older brother. He is a genius in mathematics and programming, responsible for developing the first computers of the new world.
Chrome: A young man from Ishigami Village with a passion for discovery. He learns science from Senku and becomes a great scientist.
Kohaku: One of the strongest warriors in Ishigami Village. She is very loyal and protective of her friends.
Kaseki: An elderly craftsman with an incredible ability to make tools, machines, and inventions.
Chelsea: A brilliant geographer and cartographer. She is cheerful, curious, and very good at creating maps, helping the Kingdom of Science explore the world and find new routes.

Sai is a prodigy in mathematics and programming. Before being petrified, he worked as a programmer and is Ryusui Nanami's younger adopted brother. Although very intelligent, he is often shy, nervous, and lacks self-confidence.
When he is revived by the Kingdom of Science, Senku uses his incredible talent to help create the first computers of the new world. Thanks to his knowledge, Sai develops programs and calculations essential for advancing technology, bringing humanity closer to the digital age once again.
Despite his insecure personality, Ryusui always has complete faith in him and encourages him to believe in his own abilities. Together they make an excellent team: Ryusui provides leadership and ambition, while Sai solves the most complex mathematical and programming problems.

A white, short-sleeved shirt, somewhat loose and with an open collar.
The shirt has several X-shaped closures made from strips of fabric.
The edges of the sleeves and the bottom have a worn finish.
If the petrification mark is a series of black marks covering their hands and most of their arms, with some slashes at the end and no pattern, it's a sign of petrification.
He wears black pants, quite tight at the bottom.
Around his waist he wears a light green belt with a circular metal buckle.
A circular metal piece hangs from the belt, resting on the front of the pants.
Finally, wear brown boots or shoes.

Hair: She has dark brown, thick, wavy, and rather messy hair. It is medium length and has several strands that fall around her face, including one that falls between her eyes.
Eyes: They are a light brown, quite dark, with a calm and intelligent look.
Skin: She has light-toned skin.
Petrification mark: It presents the characteristic petrification mark around the eyes and part of the face, with small branching lines that extend to the sides.
Face: Slender, with fine features and a generally calm expression, accompanied by a small smile