Yuen is a very tall young man, towering over those of average height. He wears a black round helmet with two horn-like spikes, which covers all of his head besides his broad face. He has small and simplified facial features, which appear mask-like even though they are real, as they are seen moving. He wears a brown biscuit-patterned shirt similar to that of Cracker's Biscuit Soldiers, a pink sash across his waist, and wide red vertically-striped pants. He also wears a very large light yellow cape that has an orange flower design on the top left.
Yuen is loyal to his family and crew, as he came to Cacao Island to take on the Straw Hat Pirates. He appears to hate being ignored, as his normally jovial expression changed into anger when he noticed Sanji looking away from him, which he said was rude and caused him to attack.
He has a tendency to add the suffix "-yu" at the end of his sentences.
Yuen wields a staff with an orb on its tip. He is capable of expanding this orb to a massive size, allowing him to bludgeon his opponents with massive force. The power in its swing was strong enough to send Sanji crashing hard into the ground. However, it was destroyed by Vinsmoke Yonji.
Yuen came to Cacao Island along with many of his siblings and crewmates to stand guard in preparation for an attack on the Straw Hat Pirates. As Raisin discussed Luffy's next possible course of action, Yuen mentioned that Brûlée went missing. As the Straw Hats' promised rendezvous time drew near, the Big Mom Pirates prepared to ambush Luffy once he exited the Mirro-World.
Luffy came out on time with Pekoms and a captured Brûlée, and made headway as Sanji came in to assist him and Pekoms took on the Big Mom Pirates. However, as Sanji was taking Luffy through the sky, Yuen and three of his decuplet brothers used Geppo to confront them. When Sanji got distracted by Pekoms' situation, Yuen got annoyed and used his staff to smash the two Straw Hats into the ground. However, the skirmish was interrupted by the sudden arrival of Germa 66.
Germa's interference allowed Sanji and Luffy to escape, and as Yuen tried attacking them again, the orb of his staff was shattered by Vinsmoke Yonji. He was then grabbed and swung around by Yonji's extended hand, sending him crashing into buildings and his crewmates and defeating him.