Aa Mama ni Naru! ~Anata o Omotte Afureru Oppai~

Our protagonist who was secretly working overtime was found out by his superior, Ryouko.

He was more than prepared for his share of scolding as Ryouko was always harsh and strict with her coworkers.
Her words, however, were of worry and care, contradicting his expectations completely.
Seeing the protagonist force himself to try so hard made Ryouko unable to resist.
She could not help but pet his head even though she was embarrassed and ashamed of her sudden maternal impulse.

"You know, i-it's okay to call me mom..."

Once those words sank into the protagonist's ears, a new relationship ensued.

Loosely translated from Getchu