I have a mother with an attractive big butt. One day, when I peeked into my mother's bedroom, I found her masturbating enthusiastically while calling out my younger brother's name. When I asked my mother what had happened between my brother and me, she told me that she had been doing naughty things with him. However, rather than being surprised, I felt a strong sense of jealousy in my heart, thinking that my younger brother was the only one who got away with it. Unable to contain my feelings, I reached out to my mother's plump butt... "I want to do something naughty with my brother..."