Grandfather's Gundam is the 29th episode overall and the first episode in the Kio Arc of Mobile Suit Gundam AGE
Right after his son's birth, Asemu Asuno leaves for his final mission and is listed as MIA. Thirteen years pass and Asemu's son, Kio Asuno, has grown into a gentle young boy, who hasn't experienced war so far. All that changes when his hometown of Olivernotes is attacked by the Vagan, following Big Ring's destruction by the enemy's mobile fortress and the Vagan leader, Fezarl Ezelcant, declaring a full scale invasion of Earth. The Vagan attacks stretch over the entire planet and the whole Federation falls into chaos. Amidst the danger, Flit and Kio activate a new Gundam, AGE-3, in order to defend Olivernotes.