Harold is one of the five Morino quintuplets, born alongside his siblings on the same day. His personality is distinctly intellectual and serious, defined by a powerful focus on academics and a determined ambition to win a Nobel Prize. This scholarly dedication differentiates him within his family.

He actively engages in the quintuplets' shared adventures and daily misadventures. Despite differing personalities and conflicts, Harold collaborates with his siblings when situations demand collective problem-solving or teamwork. His bookish nature and methodical approach frequently contribute to the group's dynamics during these joint experiences.