Dakara Botan ga Suki Yanen

Botan, an elementary student, lived with her ill mother, Sakura. Botan's father passed away in a car accident. One day a strange man named Miyuki appeared in their lives and her mother married him. Even though Botan hated Miyuki for ending her time alone with her mom, Botan accepted him for her mother's sake. Later on, Botan overheard Sakura and Miyuki's conversation and found out her real father was Miyuki after all.

Sakura's illness worsened until she died. Miyuki, having lots of debt from a failed business, decides he doesn't want Botan to have a hard life and tries to leave her behind. But Botan declares that they can never seperate and their new lives as vagabonds begins.

(from mangaupdates)