This is the form Justice Gundam takes after being recognized by King Guardian Sanborn, becoming another King of Britis, the "Holy Shield King." He unleashed the true power of the divine sheath Invincible, neutralizing the magic of Zeon and leading the Knights of the Round Table to victory with their light power.
Respecting his brother's wishes, King Gundam V decided to rule the Britis Kingdom. Originally a genius with a pleasant personality and high charisma, he was arguably the most suitable person for the throne.