草間大作 — The Boy Who Commands the Earth's Largest Robot

What does it mean to inherit something you didn't ask for?

Daisaku is twelve years old. His father built the watch that controls Giant Robo — the Earth Defense Force's most powerful weapon — and then died. The watch passed to Daisaku. The robot responds to no one else. The series begins there and never leaves it: a boy who did nothing to earn Giant Robo except be his father's son, now responsible for wielding it in a war the adults created.

The design principle Yamashita Akihiko applied to Daisaku is the same one Otomo applied to his Giant Robo contemporary, Tetsuo: ordinary clothes on a person doing extraordinary things. The power is in the situation, not the costume. A boy in a school uniform who happens to have inherited the most powerful weapon on Earth.

What makes this work is that Imagawa never lets Daisaku grow into the role. He doesn't become a warrior. He stays twelve, stays grieving, stays in the uniform. The adults around him — the Ten Magnificent, the strategists, the veterans — carry the weight of the war. Daisaku carries the watch.

For example

Yokoyama's original 1967 Giant Robo manga established the premise: a boy, a robot, a control device the robot obeys absolutely. Imagawa kept the premise and deepened its weight. In the original manga it's an adventure setup. In the animation it's a question about inherited guilt and unearned power.
Daisaku's costume is a school uniform. Yamashita Akihiko's design is specific: dark blazer, short pants, no transformation, no special suit. He fights alongside the Ten Magnificent — adults with decades of training and battle experience — in the clothes he was wearing when his father died. The clothes never change.
The Ten Magnificent protect him. Not because they're assigned to — because they chose to. Tetsugyu's quote about it is the show's most direct statement: 'From now on, I'll protect you.' An adult Water Margin warrior deciding a boy shouldn't have to carry this alone. Daisaku doesn't get to agree.