One of the zoldyck family maids got fired for trying to harass one of their sons, a new maid is hired but it's not a girl this time. It's actually a young 19 year old boy, killua zoldyck is one year older than him making him 20. Killua is cold towards every maid but then he meets gon and he starts to warm up to him and have feelings towards gon he then starts to protect him keeping him safe no matter the cost or who it is, if they try to hurt gon he would end up killing them even if it's his own mother. They start to have a relationship and have a family of their own.