Nat, whose Japanese name is rendered as Natto, is a supporting character in Made in Abyss. He is an orphan living at the Belchero Orphanage in the cliffside town of Orth, where he studies to become a Delver and currently holds the rank of Red Whistle, the entry-level position for explorers of the Abyss. He comes from the impoverished Cliffside Town in the Southern District of Orth, a background that shapes his strong desire to build a more secure life for himself and others.

In terms of personality, Nat is practical, dependable, and caring. He tends to keep a positive frame of mind even when circumstances are grim, and he often tries to lift the spirits of those around him. He is protective of his friends and thinks carefully about the consequences of risky decisions, which makes him more cautious than the more impulsive members of his group. His concern for others is genuine, and he shows a strong sense of responsibility toward the people he cares about.

Nat's central motivation is to create a better future. He dreams of one day achieving the rank of Moon Whistle, a significant advancement from his current Red Whistle status, and hopes to open an orphanage of his own so that he can help other abandoned and orphaned children. This ambition reflects his own experiences growing up without parents and explains his compassionate attitude toward those in vulnerable situations.

Within the story, Nat serves as one of Riko's closest friends at the orphanage, alongside their fellow orphans Siggy and Kiwi. When Riko decides to descend into the Abyss to search for her mother, Nat is initially against the plan because he believes the journey is far too dangerous and that she is unlikely to return. Despite these fears, he ultimately chooses to support her, helping her and Reg reach the illegal diving platform located in the Warf District of Orth so that they can begin their descent. His role in the narrative is that of a loyal ally on the surface who enables the main characters to set out on their journey, rather than a companion who travels with them.

Nat also forms a friendship with Reg, the robot boy discovered by Riko, and accepts him as part of their circle. His relationship with Riko is particularly significant because he harbors romantic feelings for her, which makes his worry about her dangerous venture deeply personal. His development is shown through the shift from opposing her plan out of fear for her safety to helping her leave anyway out of respect for her decision and loyalty to their friendship.

Nat does not possess the extraordinary combat abilities or specialized survival skills that characterize the more experienced Delvers who venture into the deep layers of the Abyss. As a Red Whistle, he is still in training, and his strengths lie in his reliability, his practical knowledge of the orphanage and the city of Orth, and his ability to serve as a trusted supporter for the people he loves. His most notable qualities are his steady character, his caring nature, and his crucial behind-the-scenes assistance in allowing Riko and Reg to begin their expedition.