The art features the soft, classic "moe" style of the early 2000s, emphasizing large, expressive eyes and a gentle color palette.
For a series released in the mid-2000s, the production quality is a hallmark of the era’s aesthetic. Aneki... My Sweet Elder Sister- The Animation
Despite being decades old, this series is frequently cited in discussions about the "Onee-san" (older sister) trope for several reasons: The art features the soft, classic "moe" style