Her daughter. The princess of earth and moon in the 30th century. The troublesome child who stopped growing at age of six and without power till after she went over 900 years. The girl who has a huge Electra complex (father complex) and tries to actually compete with her own mother for the love.
At the beginning Usagi doesn’t actually know what to do about her, and Chibiusa also doesn’t really have clear ideas about it, because she doesn’t at all acts like she knew that Usagi and her mother are actually the same person, just one is only 15 years old the other one has over 900 years.
Those two seem to argue really much, they seem more like sisters than mother and daughter, even if in the future the pink haired one acts differently toward her mother.
Anyway, the relationship between the two is great, even if it doesn’t
seem both care deeply for each other and would do everything to protect each
other from the evil. Even more Usagi, who maybe doesn’t seem to act as
one, but she is really protective when it comes to Chibiusa and is prepared
to risk everything for the one who in the future will be her daughter.