START-587 Rui Ichimiya

Orphaned at a young age, a brother and sister relied solely on each other. When the sister grew up and introduced her fiancé, the brother was initially happy for her. However, witnessing his sister being intimate with her fiancé ignited a fierce jealousy within him. Driven by this, he repeatedly engaged in sexual acts with his sister, impregnating her, as they both vowed to stay together forever.