The older sister is notably tall (over 170cm), creating a literal "looking down" visual that emphasizes the power imbalance between her and the protagonist. The "M" Personality:
In the world of Japanese adult media, production labels like use these codes to categorize their massive libraries. The "SSIS" prefix belongs to this major studio, known for high production values and featuring some of the industry's top "exclusive" actresses.
The "taller older sister" trope is a central marketing point, emphasizing the visual of the male protagonist having to look up at her. Narrative Style: