This is an odd scenario - which is what you'd expect from another secret scenario. Goldry challenges you to a game of Langrisser in the arcade (!), so there's little else for you to do but play him.

Before the fighting begins, he asks you in which order you wish your characters to fight. You cannot choose Sigma, so the order in the list is Marie (Lambda), Alfred, Brenda and Claret. Once you have chosen in what order these four fight, you will start the game.

Whoever you chose first will be pitted against one of the enemy generals, which are picked seemingly at random. Once (if) you defeat them, the next general will fight you, and so on. Beware, there is a time limit of about 8 Turns, I think. The last character to fight is Goldry himself, and he has some particularly nasty units to contend with. Dragoon in particular would need Phalanx or a lot of Pikemen to deal with.

None of the items in the shop seem particularly worth having, especially at those prices. I always prefer to save up, should I need to use some particularly expensive troops (Snow Dragons or Shades, for instance).