Well, 'Am a Child of This House' manga tells the story of a kid in a house where there are both fun and tough times. It's about their friendships, family bonds, and personal development. It's a story that will make you laugh and maybe even shed a tear.
Another good one is 'The Little Prince'. Although it's often thought of as a children's book, it also exists in light novel form. It tells the story of a little prince who travels from planet to planet, meeting various strange characters and learning about love, friendship and life in a very philosophical way.
I need more context to answer your question. Please provide more background information, such as the original story of this child and the plot of this child and the original story, so that I can better answer your questions.
Well, it's not really about age. It's more about the characters' feelings and circumstances. Some manhwas might challenge the idea of age and focus on true emotions instead.