Souryuu and Hiryuu, being originally designed as sister ships, share many similarities. Namely, they wear color-differentiated versions of the same clothes.
She wears a yellow kimono top, with the bottom of the sleeves fading to gray with red stripes. Her bottom is a green pleated skirt. She also wears a flight deck apron like Akagi and Kaga (The kana "ヒ" is inscribed on it). Her full flight deck is attached to her left arm. Unlike most other archer carriers, she doesn't wear muneate.
For her Kai ni remodel, she is given a headband, a slight tan as well as a massive firepower boost amongst other stats increases.
Hiryuu is a favorite subject in artwork featuring both Ship Girls and their actual commanders in WWII. In her case, she's usually shown with the famous Yamaguchi Tamon, who, according to reports, went down with her while calmly admiring the moon with her captain Kaku Tomeo. Many of Hiryuu's ingame lines also contain references to Yamaguchi.
