Isamu Amami is a 35-year-old human male with brown hair and brown eyes, typically depicted wearing glasses. He works as a computer operator and is married to Ai Amami, forming a central family unit.

In 1997, near the North Pole, Isamu and Ai received an infant named Latio from Galeon, a mechanical lion from space. They adopted the child, renaming him Mamoru ("to protect"), and raised him on Earth. The couple safeguarded a pendant left with Mamoru by Galeon, unaware of its importance or Mamoru's extraterrestrial origins.

During the Zonder invasions starting in 2005, Isamu and Ai supported Mamoru as his latent power to purify Zonder cores emerged. They maintained a stable home life while Mamoru served as a "special agent" for the defense organization GGG.

After the defeat of the 31 Primevals and 11 Sol Masters, Mamoru returned to Earth and married Hana Hatsuno. This union made Isamu and Ai grandparents to Mamoru and Hana's son, Tsubasa.

Isamu remains a steadfast family figure, with no involvement in combat, special abilities, or occupational shifts beyond his computer operator role.