OVA
Description
Yuuji Kashima is a shy adolescent marked by timidity and a lack of confidence. He lives with his mother, Aoi Kashima, and older sister, Yuri Kashima; his father is absent, leaving the family unit as just these three.

Yuuji's defining characteristic is his profound affection for his family, especially his mother. This devotion drives his initial choice to play an unfamiliar board game offered by a mysterious salesman. The salesman presented Sōkan Yūgi as a tool to strengthen family bonds, appealing directly to Yuuji's wish to bridge emotional gaps at home.

Sōkan Yūgi exerts a supernatural compulsion on its players. Once started, participants become trapped within the room and unable to refuse instructions. The game requires landing on colored spaces and drawing cards that command specific intimate acts. Landing on red spaces strips Yuuji of all bodily autonomy, forcing absolute compliance with the card's demands against his will.

During gameplay with his mother, Yuuji displays reluctance towards the escalating intimacy the game demands. Despite his resistance, the supernatural curse compels him to perform increasingly sexual acts, beginning with embraces and kisses and progressing to intercourse. This occurs contrary to his original intention of achieving non-sexual closeness; the supernatural enforcement crushes all hesitation.

After this encounter, Yuri learns of the incident through a dream. This knowledge alters her behavior towards Yuuji. While their past relationship involved frequent arguments, Yuri begins to feel sexual attraction for her brother. While masturbating in the bathroom and thinking of Yuuji, she resolves to initiate another session of the board game with him to forge a similar closeness between them. This marks the start of further compelled sexual encounters between the siblings.

Yuuji demonstrates no active pursuit of these sexual relationships beyond his initial, misled acceptance of the game. His involvement in all subsequent intimate acts stems entirely from the game's supernatural control or the initiation by others. The narrative portrays him as consistently subject to external forces throughout these events.