My Mom Is Mano-kun.

After losing her mother, Mizuki Kamo is the eldest daughter, raising her younger siblings on her own. Mizuki tends to be relied on by those around her, but in reality, she wants someone to pamper her. Then, her motherly colleague, Mano-san, appears before her. Although he is a good-looking man, he is also caring and tolerant, and Mizuki can't help blurting out, "Please be my mom!" A heart-warming and heart-fluttering romantic comedy filled with love and doting begins! (Source: Akita Shoten, translated)