Sobo no Kami wo Kitta Hi

Shikabane never knew his mother. Abandoned by his father, he lived alongside his grandmother as a child in poverty. But thanks to the kindness of the latter, despite a difficult daily life and the blessings of his comrades, he managed to grow and build himself. As an adult, he finally believed he could enjoy life. Unfortunately, when his grandmother seems to show signs of senile dementia, Shikabane loses his footing and doesn't know how to react...

(Source: Akata, translated)