Two people became siblings due to their parents' remarriage. The younger brother, in his puberty, can't suppress his sexual desires. Initially, the sister was just helping him with masturbation... 'Are you going out with that guy?' 'I won't give you my sister!' As the brother's jealousy grew, they unknowingly crossed a line. However, when faced with difficulties, the brother tries to give up their relationship. 'You worthless brat, drink your sister's piss!' The sister's emotions explode, leading to forced internal ejaculation... 'Sumire Onee-chan's smile is the cutest and most destructive!' Plus, 'She's slender, fair-skinned, and has pink nipples!' If you suddenly have to live under the same roof as a sister like this...
