Haruka Yoshino is a teacher at the 62nd Higher Training School, serving as a homeroom assistant. She holds a unique position within the school as the only civilian among the main cast of pilots and military personnel. Her academic focus is on the Korean language, though she also teaches various other subjects alongside her colleagues.

In terms of personality, Haruka has a somewhat natural or airheaded impression, giving her a gentle and approachable demeanor that feels more like an older sister to her students rather than a strict authority figure. However, this soft exterior masks a deeper fragility. She is mentally vulnerable, a trait that becomes more pronounced under the stress of her environment.

Her primary role in the story is to provide a non-combatant perspective within a world dominated by military conflict. As the students she cares for are sent into dangerous missions, Haruka is deeply affected by their deaths. She struggles to cope with the resulting feelings of shame and powerlessness, frequently turning to alcohol as an escape mechanism. This pattern of grief and drinking is a central aspect of her character development, leading to an eventual mental breakdown.

A critical element of her background is that she is a clone. In the setting of the fifth world, biotechnology and cloning technology are highly advanced. Haruka is one of many mass-produced clone units specifically created to fill the role of a teacher. Because of her mental frailty, her inability to handle the death of her students is a recurring issue. When she inevitably breaks down from the pressure, another identical clone of the same type is simply brought in to take her place as the teacher, resetting the cycle. As a civilian, she possesses no notable combat abilities. Her key relationships are with her students, whom she views as charges to protect, and this maternal, sisterly bond is the primary driver of her tragic narrative arc.