There were few things an infant could do.
They received food from their mother, slept according to instinct, and did their business.
It was just these three at most.
However, Luru had what infants normally didn’t; a strong ability to think.
Because of that, he was able to consider thing, and arrange the information he heard from perking his ears up.
From the time when he clearly recognised that he held his memories as the demon king, each day he would listen up for the conversations that went on in his home, and a number of facts became clear to him.
What he learned about in most detail, was of course, information about his own family.