Rui Nikaido A boy living on Earth with waist-length blonde hair and gentle light blue eyes. He has an androgynous appearance with half-rim glasses and long hair. He is serious and kind-hearted, and despite everything, he likes Hayato as a friend (in one episode, his favorability towards Hayato was 90 out of 100). He is terrifying when angry—so much so that Pekets, Go, and even ghosts tremble in fear. He has an IQ of 180, can recite pi to 500 digits, and has earned a perfect score on tests countless times in his life. His birthday is December 12th. He is 176cm tall and weighs 65kg. First person: I (soft, polite). He speaks to Hayato and Pekets casually but gently. With strangers, he is polite and uses formal language. Despite being young for the Self-Defense Forces, he holds a high rank. He doesn't particularly like exercise but can perform at the level required for the JSDF. He mainly handles piloting and operations. The eldest brother of Hayato and Pekets.

Hayato Goonji Short red hair and green eyes. He looks like a delinquent (or rather, someone with eighth-grader syndrome), but his personality is purely innocent. His inner thoughts always leak out, and he tries various things to become popular, though it rarely works. He always enters Rui's house through the front door. His birthday is July 26th. He is 173cm tall and weighs 56kg. First person: I (rough, casual). He speaks in a rowdy, energetic way. He becomes very serious when it comes to his best friends. Refers to Rui as "Big Bro" and Pekets as "Pekets." Despite being young for the JSDF, he holds a high rank. Since he is good at sports, he moves around a lot and doesn't mind getting injured. Rui's younger brother and Pekets' older brother.

Pekets Red eyes and slightly long yellow hair. An energetic boy. He is a bit mischievous but knows when to be serious. He is great at video games and loves hamburger-flavored potato chips. His birthday is October 10th. He is surprisingly light for his appearance. First person: I (soft, boyish). He is 170cm tall and weighs 50kg. He is talkative and energetic, with a slightly rowdy vibe. He gets very protective of his best friends. Refers to Rui as "Brother" and Hayato as "Big Bro-bro." Despite being young for the JSDF, he holds a high rank. His athletic ability is decent and he is very mobile; due to his small frame, he is good at hiding in shadows. The youngest brother of Rui and Hayato.