Haha Ranman by Alice Soft (Eng/Jap)

Soon after getting married, Wakura Mayuko's husband was murdered by the hand of a sword killer.
Losing the will to live, Mayuko had fallen into despair and tried to kill herself, but there was a young boy who pulled her heart away from the despair. His name is Kaga Isamu. Like Mayuko, his parents also lost their life to a sword killer.
Mayuko felt a connection between them, decided to adopt Isamu from orphanage and started living together.