Taizo Nonomura is Shun Nonomura's father, a first-generation lunar colonist residing in Level 3, a neighborhood for third-generation Lunarians. He maintains a non-confrontational stance toward the rising tensions between the Moon colonists and the Earth Federal Government. Taizo prioritizes family safety above political involvement, a position contrasting with his older son Tatsuya's rebel activities and his younger son Shun's growing entanglement with the resistance.

During an outing to Level 3's park with Shun, his wife Rachel, and his own father, another first-generation colonist, Taizo demonstrates conventional family bonds. His presence at Shun's arrest by Earth forces underscores his role as a concerned parent navigating oppressive circumstances. Taizo represents the generational divide among the colonists, embodying the older generation's connection to Earth as their ancestral homeland despite its exploitative policies. His character highlights the internal conflicts within lunar families amid escalating rebellion.