As a child, Hatsuharu Sohma was already known within the Sohma family for having a reputation as someone who was somewhat unintelligent or foolish. This perception was directly tied to the zodiac legend, in which the rat tricked the ox into arriving last to the banquet, thereby losing the first place in the zodiac order. Young Haru internalized this story and specifically blamed Yuki Sohma, the current vessel for the spirit of the rat, for his own resulting reputation.

This childhood resentment led Hatsuharu to confront Yuki directly. He expressed his anger, believing that Yuki was the cause of him being called names. Yuki did not respond with anger but instead asked a simple question, asking Hatsuharu if he truly believed he was a fool. This simple inquiry was a revelation for the young boy. He realized that the opinions of others did not have to define his own sense of self, and that he was trapped by a legend rather than any personal failing. From that day forward, his feelings transformed entirely; he let go of his blame and developed a deep and enduring admiration for Yuki, later referring to Yuki as his first love.

Even in his youth, the foundations of his famous dual personality were present. His two-toned hair, white with black roots, signified the two sides of his nature that would become more pronounced with age. The Sohma family would refer to his calm, placid state as his "white" side, and his enraged, violent state as his "black" side. It was later disclosed that this "Black Haru" personality was born as a defense mechanism to help him cope with the mockery and insults he received from other children for his unusual appearance. While Kisa Sohma, another zodiac member who was bullied, would retreat into silence, young Hatsuharu would turn "black" and chase his tormentors around the schoolyard or even fight them. This established his pattern of being immensely loyal and protective of those he cares about, a trait that would define his relationships as he grew older.