Sae Shingyouji, Shinji’s childhood friend and romantic partner, shares a deeply rooted bond forged through years of growing up together. Central to her identity is a solemn vow to abstain from sexual activity until marriage, a commitment that shapes her relationship with Shinji and fuels the story’s tension. This promise collides with external pressures Shinji faces to secure his grandfather’s inheritance by identifying a woman bearing a unique birthmark—one revealed solely after sexual climax. Speculation mounts over Sae’s potential link to the birthmark, pitting her steadfast principles against the urgent demands of Shinji’s quest. While narrative clues imply she might harbor the mark, its emergence would defy her chaste pledge, leaving her role suspended between possibility and paradox.

Orphaned alongside Shinji, Sae’s past remains shrouded beyond their shared upbringing and her unwavering focus on their future. The narrative prioritizes her connection to Shinji over exploring her personal history, aspirations, or individual growth outside their partnership. Though unresolved plot threads hint at her potential involvement in the birthmark mystery, the series’ incomplete adaptation leaves these questions unanswered.

No supplementary portrayals in alternate media expand her character, as existing sources confine her arc to the original OVA series.