SD Gundam Gaiden: Knight Gundam Monogatari 2: Hikari no Kishi is the second installment in the Knight Gundam series. It takes place in a universe in which the Gundam characters are reimagined as knights, wizards, kings and other medieval type characters. This game is a direct sequel to the first game, so you ought to play through the first one first. It may seem unrelated at first, but the story converges with the first game’s eventually.
