Yuuta Segawa, a university freshman, finds himself entrusted with the care of his nieces Hina, Sora, and Miu after a tragic incident claims their parents' lives. With echoes of his own past, Yuuta steps into the role of guardian, defying conventional norms to keep the family together. Amidst the backdrop of the Street Observation Research Society, where Yuuta is a new recruit, he navigates the delicate balance between his club activities and newfound fatherly duties, while the girls grapple with their profound loss.