As Mengsk's Uprising began to escalate, Arcturus Mengsk later hired Miyamoto to teach his son, Valerian, when he had to continually move him around to avoid Confederate agents. Miyamoto taught the child academics and various forms of fighting. He ensured that Valerian learned concepts such as honor. Miyamoto hailed Valerian as his best ever student when it came to using a sword.
While there, they were struck by a surprise attack launched by the Confederate Resistance Forces. A number of Wraiths and 30 marines led by Captain Angelina Emillian had come to Umoja, seeking to kill Arcturus Mengsk. They heavily outnumbered the Dominion and Umojan defenders.
The Mengsks and Miyamoto took shelter in a landing bay and crashed ship. Miyamoto fought back with his rifle and suffered injuries, eventually falling to a shot in the back from Emillian. Valerian Mengsk and Emillian faced each other, and Emillian clearly had the upper hand, but Miyamoto wasn't dead yet. With his last strength he damaged her gauss rifle with his sword, enabling Valerian to shoot her down.