Introducing the Onii-chan wa Oshimai! Oyama Mahiro Mizugi Ver. figure by Ichigoichie no Hijinks. The swimsuit version showcases Mahiro's playful charm through a sunlit pose on a coral base, with a detailed bikini that features crisp lines and vibrant color blocks. The sculpt captures the character's slender silhouette, with subtle muscle definition and delicate facial expression, framed by short, wet-looking hair and a buoyant, excited stance. The paintwork emphasizes glossy swimsuit panels, shading on the skin, glossy eyes, and tiny accessories like a shimmering charm on the hip. The overall presentation radiates summer fun and lighthearted mischief, making it a standout display piece.

Oyama Mahiro, the central figure of the series, finds his ordinary life upended when a magical mishap swaps his gender temporarily and thrusts him into a world of playful magical mischief. As he navigates new social dynamics at home and school, he learns to adapt to unfamiliar situations, uncover hidden powers, and rely on friends and family to help him maintain his identity. Throughout the story, Mahiro's daily challenges—classroom etiquette, sports, and friendships—are peppered with humor, candid moments, and heartfelt growth, highlighting resilience, acceptance, and the bond between siblings in a whimsical fantasy setting.