Mao-chan is a cheeky high school girl who loves to tease her virgin big (step)brother in naughty ways. However, her true intention is actually...?(Source: (https://booklive.jp/product/index/title_id/20063387/vol_no/001))---Note: the original Pixiv series has been collected and published into 2 volumes.Volume 1 (上) "Up" contains chapters 1-20. Volume 2 (下) "Down" contains chapters 21-42.