Itadakimasu, no Mae to Ato(2020)

Itadakimasu, no Mae to Ato

When Mitsuba was in elementary school, her mother gave her a single lunch box and sent her to live with her grandfather.
However, now that she is a high school student, Soma, an elementary school student claiming to be her younger brother, arrives with her mother's bones. With the help of Kai, an aspiring novelist from the neighborhood, they have proper funerals. Mitsuba then decides to live with Soma, who has the same memory of her mother's food.
Discover the story of Mitsuba, the older sister who has forgotten her mother, and the younger brother left behind by her, who have one thing in common: memories of delicious food!

(Source: Kodansha, translated)