Shii Aasu, the fourth of seven sisters entrusted with Earth’s defense, bears a name rooted in the Japanese word for "four" (*shi*), marking her birth order. Eighteen years old, her most striking feature is her exceptionally large breasts, each weighing 8000 grams. Chronic back pain from their size drives her to rest them on surfaces or unsuspecting individuals, including Poemi Watanabe, whose head becomes a frequent support after joining the household. Shii champions Poemi’s residency primarily for this physical relief.

Her breasts fuel recurring humor and mishaps, such as accidentally smothering the family cat. Their heightened sensitivity triggers exaggerated reactions when touched, contrasting Shii’s pride in her figure. She openly teases her sisters about their smaller statures, flaunting her physique with playful confidence.

As an Earth defender, Shii wields Earth Healing magic, a strictly defensive ability shared among her siblings. While her role leverages this power, narrative emphasis often shifts to her comedic struggles and physical traits. Her personality blends mischievous teasing with pragmatism, addressing discomfort through solutions like recruiting Poemi.

Residing with six sisters—each numerically named by birth order—Shii collaborates with them to protect Earth, though their non-offensive magic limits confrontational tactics. Family dynamics and teamwork against threats anchor her interactions, balancing situational humor parodying exaggerated femininity and comedic sensuality with their shared duty.