Tensei shitemo Jikka wo Oidasareta node, Kondo wa Jibun no Ishi de Ikiteikimasu

The protagonist, who lost his life in an unfortunate accident while returning from a part-time job, is reincarnated as a baby named Alex in a fantasy world. Having been abandoned by his birth mother in his previous life, Alex decides to live freely this time. However, he learns that he’s destined to be abandoned in this life as well. Alex intensively trains in magic with Liz, his adorable little sister figure who shares his fate! Even when they're left behind in a deep forest on the fated day, they aim to escape using the magic they've mastered together. The two little ones make it past the forest to the Hohenheim domain. They have great adventures, starting their lives as adventurers with Jin, a kind young man they meet by chance, and even saving the town from a horde of monsters! Meanwhile, an evil plot is unfolding in their family home...!?

(Source: AlphaPolis, translated)