Since moving to his brother and sister's house to make it easier for him to study, the younger brother couldn't help but notice his lustful sister-in-law Yui Hatano. She has sexy big breasts, a smooth body and is especially very lustful, which is what makes him constantly spy on her, secretly peeking at her when she shows her lust outside. The story would not be worth mentioning until he accidentally caught his sister-in-law masturbating in the bedroom, curiosity urged him to stand outside the door and peek for a long time and then bad luck struck, he was discovered by his sister. Panic and fear were the first feelings he felt, thinking that he was at high risk of being kicked out of the house, but no, in bad luck there was good luck. She gave him a very light punishment, mainly to satisfy his unquenched lust, which was to agree to incest with her. Because he was so scared, the young boy had no choice but to reluctantly accept the request of his lustful older sister.