This characters are part of the story, but they aren't able to be used in battle nor able to support you in one. Most of them only give you quests or are shop owners (some both).
“Warren (ワック Wack) is a boy who stays at Ariela's Tavern. He is sick when Dagran's Mercenaries...Warren
“Unnamed Captain is the current captain of the Lazulis knights. He is fairly rude to Zael and the...Captain