Kyoudai dakedo Giri da shi Irenakereba Ecchi ja Nai yo ne

Hanahito has a cute and easygoing step-sister named China. He harbors forbidden feelings for her and struggles with the habit of masturbating while watching her take a nap. However, one day, he accidentally stumbles upon China herself masturbating. Will this obsessive guy with a yandere streak lose all control?

(Source: Ichijinsha, translated)