Masaki Andoh is a 17-year-old male orphan from Japan on Earth, burdened by deep-seated loneliness. Summoned to the subterranean world of La Gias, specifically the Holy Langran Kingdom, he became a pilot for their biomechanical Masōki weapons. This summoning occurred because La Gias inhabitants generally lacked sufficient "prana" (life energy) for effective Masōki operation, while surface dwellers like Masaki possessed the necessary "violent prana" fueled by intense emotional fluctuations.

Initially assigned the Wind Masōki, Jaohm, Masaki's athleticism and emotional volatility made him suitable, especially for higher-tier Masō Kishin (Elemental Lords) requiring high prana. He was mentored and adopted by Zeoroot Zan Zenoskis, receiving the Langran name "Randoll Zan Zenoskis" linking him to an ancestral hero. He formed a close sibling bond with Zeoroot's biological daughter, Presia Zan Zenoskis.

Masaki's path pivoted when the semi-sentient Masō Kishin of Wind, Cybuster—blessed by the wind spirit Cyfis and created by Langran to combat threats like the Volkruss cult—chose him as its pilot after being stolen by Shu Shirakawa's follower, Saphine Grace. Bonding with Cybuster granted Masaki two familiar cats: Kuro (black, female) and Shiro (white, male). These familiars assist in operating Cybuster's "High Familiar" weapons and constantly mock his complete lack of directional sense, which prevents him from pursuing fleeing enemies despite Cybuster's speed.

Shu Shirakawa became Masaki's nemesis after betraying Langran, killing Zeoroot, and fleeing to Earth with his powerful Granzon. This defined Masaki's core motivation: pursuing Shu across dimensions to stop his destructive schemes, viewing him as a threat to all life. While initially driven by vengeance, their interactions evolved during conflicts against entities like the Einst and Volkruss, leading to a reluctant alliance against greater threats, though Masaki remained quick to blame Shu for calamities.

Masaki struggles with social interactions, particularly around women, leading to comedic situations despite attracting romantic interest from Cybuster's designer, Wendy Rasm Iknart, and Lune Zoldark, daughter of Divine Crusaders founder Bian Zoldark. Lune proclaims herself his girlfriend, while others like Becky note polygamy's commonality in La Gias, causing him embarrassment. This dynamic, alongside his loyalty to Wendy and protective feelings toward Presia, forms an unofficial "harem" context.

After Langran's destruction, Masaki frequently traveled between La Gias and Earth, aiding surface organizations like the Earth Federation Army and the crews of the Hagane and Hiryuu Kai battleships during crises such as the L5 Campaign and conflicts against remnants of the Divine Crusaders and extraterrestrial invaders like the Aerogaters. He leveraged Cybuster's capabilities, including dimensional travel and high-powered attacks like the Cyflash, while navigating his directional impairment with unreliable guidance from Kuro and Shiro.

Masaki's character arc emphasizes growth from a solitary, hot-blooded avenger to a protector burdened by duty. His status as a Masō Kishin Herald grants him autonomy to oppose any Langran ruler threatening peace, reflecting his innate sense of justice. Despite comedic traits, his core resolve stems from gratitude toward Zeoroot and La Gias' inhabitants, who alleviated his childhood loneliness.