GG-265 Sister's Real Sex Education Yui Fujishima

'Yui', who has already lost her mother, lives with her father and younger brother'Ma-kun'. One day, Ma-kun is ridiculed that his friend has no sexual knowledge. After seeing it, Yui tries to teach Ma-kun sex by herself unless she teaches her mother the correct sexual knowledge. However, since then, Ma-kun has been in a good mood ...