Mama Reido vol. 3 Tomomi Mama Hen ~Usotsuki wa Mama no Hajimari~

One day, on the way home from school, Tomomi comes across Mahiro being harassed by some delinquent girls.
She warns them that she has taken photos on her smartphone as evidence.
She then calls in witnesses in the area and together they fight off the delinquent girls and rescue Mahiro.
In relief, and to calm Mahiro down after he starts crying over how pathetic he is, Tomomi takes him to her house.
As she gives Mahiro various life advice, Tomomi begins to feel aroused by the cute Mahiro,
and even though she knows it's wrong, she decides to carry out a plan she's been thinking about for a while.

[From Dlsite]