Think Yotsuba but with a planarian*/human mutant four-year-old girl instead of one with green hair.*A planarian is a kind of non-parasitic flatworm organism.
The Gang Leader Who I Thought Was a Boy Is Actually a Girl - The Kid's Leader Who I Thought Was a Boy Is Actually a Girl - ずっと男の子だと思っていたガキ大将が女の子でした - 一直以为是男孩子的孩子王其实是女孩子 -