Though he asked for her name, she couldn't answer, less speak, but Hiro saw that her code was "002." He thought of a name, first thinking "Oni" and then "Zero Two", but he wasn't particularly fond of either of those names.

What is zero twos name for Hiro?

Zero Two is an artificially-created life form who aspires to become fully human, and an elite pilot with an infamous reputation as the "Partner Killer". She is well known for addressing Hiro, the protagonist, by the eponymous term "darling".

What does Hiro call 02?

Hiro asks what her name is. She asks if parasites even have names. Her code is 002, so everyone calls her "Zero Two." A soldier says that Mistilteinn's issued a search request for him.