Muu was born on the Planet Frisney in the Chinese-like country of Janjhii, and had an older brother who fought in the Frisnean Navy for 7 years until he died in a shipwreck. This resulted in Muu's parents, who were against military work since they thought it would be too dangerous for Muu, becoming over-protective on him. He was constantly watched over by his parents, and he was even embarrassed time and time again in front of his friends by his parents constantly calling him 'Mumu'. He even had an unbearable and aggravating curfew.
When Muu finally became 18, his parents were starting to get very proud for him when he was graduating. But they ended up embarrassing him after the ceremony, which was as far as Muu's aggravation could go. After having finally snapped, Muu ran away from home to take up a job without them being very worried or stubborn. He didn't bother joining the same Navy that his brother did, and he just decided to take up a job as a swimming teacher since it's what his mother personally wanted him to do. This resulted in him falling in love with another Wachter named Kajina, who was formerly a Herizonian exchange student in his school whom he found very bland. But the problem was that she already had a boyfriend who was one of his school bullies.
After constantly failing to win her heart, he signed up for a swimming competition to impress Kajina, only to end up embarrassing himself in front of her by almost drowning and leading to the bully winning. After being rejected for the last time, Muu eventually quit his job and fled from Frisney to take up a job on Narene as a member of the Bounty Hunter Consortium. After training in 3 martial arts, he became one of their finest, but not always successful, bounty hunters. He hated it when people called him 'Mumu', especially Viume Phyarse, who heard was a weakness in him from his parents on the news on the day of his departure. However, since Xrandy defended him, the two have become close friends.
As a semi-aquatic rat, Muu can hold his breath underwater for 15 minutes. He also has a few qualities of a rat such as a flexible body and good senses. When becoming a bounty hunter, Muu was trained in 3 martial arts: Dojkibo (A Souvisian version of Hapkido), Yuqor Goah (A Seourusian martial art that specializes in pressure-point combat and aerial combat), and Uoxe Rao (A Juluwese martial art that specializes in gymnastics, balance, and pressuring an opponent). He wears an armored suit with Kevlar and uranium, and it also comes with an oxygen mask for concealing his face or for pressurized environments.
Muu carries an ISD (Infinite-Storage Device) that allows him to carry up to 7 weapons: 2 twin energy katanas, two dual Chardis TBMP-58 'Thrasher' Tri-Barrel Machine Phasers, a CCPFS-189 Pure Fusion Shotgun, an Oenopides GL-475 Grenade Launcher, and a Huncus BNG-886 Plasmablast Gun, which fires explosive blasts of plasma. He also carries a few kinds of explosives such as thermal detonators, ion detonators, flame grenades, and sticky grenades which detonates in 1 second upon skin contact. He even has some equipment such as a grappling hook, an energy bolas for retrieving people, and a hacking device.
Muu flies a spaceship called the Javelin, which is composed of theonium, a durable substance granted by the Atonts as a reward for an old service he fulfilled. It also comes with a deflector shield, and is semi-aquatic. It is propelled by 6 antimatter fusion thrusters that are powered by mini reactor cells. The ship is armed with 2 proton cannons and 2 missile launchers.