Yuuna Amatsuka ranks as the eleventh oldest among the nineteen Amatsuka sisters, being the eleventh daughter. She is eight years old and attends third grade. Yuuna displays affectionate behavior toward her newly adopted older brother Youtarou, frequently attempting to sneak kisses on him. Her fondness for magical girl-themed media is evident through her habitual carrying of a magical wand. She often engages in competitive bickering with Seika, the tenth daughter, particularly over opportunities to show affection toward Youtarou, establishing a recurring rivalry between them. During the family's promotional video outing featured in the OVA, Yuuna participates in group activities including changing into swimwear and performing a synchronized dance sequence in the end credits.