SD Gundam: Musha Maruden 2

The 14th installment in the Musha Gundam series. In “Mushu Battle,” where fighters compete under various rules, a young boy named Katsumi supports Waka (Wakagami-maru) in his quest to become the strongest warrior. Waka overcomes trials alongside his friends Bright and Hachan as they take on battles, but a conspiracy lurks beneath the surface…!(Source: Kodansha, translated)