SD Sengokuden Ten to Chi To (SD戦国伝 天と地と SD Sengokuden Heaven and Earth)
This is a side story from SD Sengokuden Musha Shichinin Shuu Hen. It happened when Musha Gundam and Musha Seita (Zeta) were having a mock battle to test the results of their training. As the battle gradually became more intense and the swords of Zeta and Musha clashed, a flash of light fell from the sky and enveloped them. Those were Sengoku warlords from another world, Takeda Shingen and Uesugi Kenshin. Their fierce fighting spirit became their souls and was transferred to each of them across dimensions.