Mao Yasaka is a Gunpla builder from Kyoto who has devoted himself to the Gunpla Shingyo school of model-building since childhood. His exceptional building skills have led many to regard him as the likely successor of that school. He takes great pride in two things: constructing high-quality Gunpla and demonstrating his abilities in battle. His appearance and the gentle Kyoto dialect he speaks give him a placid and composed impression, but beneath that surface he harbors an intense, fiery fighting spirit. He is a calm and collected presence who becomes hot-blooded and passionate when he enters a Gunpla battle. He serves as a good rival to the protagonist Sei Iori, and the two share mutual respect as competitors. Mao participates in the Gunpla Battle World Championships and also becomes involved in a confrontation with the Gunpla Mafia during an exhibition match, where his desire to impress a girl named Misaki drives him to overcome distractions and defeat his opponent. Over the course of the series, he demonstrates his growth as a builder and fighter, culminating in a climactic battle against Sei Iori. In that battle, he unleashes a powerful Demon Sword attack that gathers solar panels and satellite system energy into a beam saber, but he is ultimately defeated by Sei's Build Strike Gundam. Mao pilots the GX-9999 Gundam X Maoh, which can charge its Hyper Satellite Cannon using the moon-based Microwave System or solar power from reflective panels; later he upgrades to the XM-X9999 Crossbone Gundam Maoh. His abilities reflect both his technical mastery of Gunpla construction and his fierce, creative approach to combat.