The truth of being a mage here is somewhat useless in the earlier run, cause you would learn magic in Harmonia, after you defeat Arihama which you will learn a Praharma Skill (first magic skill drop from absorbing Arihama). Plus the the basic staff (weapon equipped) would only have a magical attack after you attend in magic school. So being a mage and battling arihama is asymptotic to say the least. They were two arcs apart. Sadly I hope that I would use spells but lore says that the MC's magic comes from Arihama himself.
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In this version 0.43. The missions will appear after you defeat Arihama. You'll enter and talk first to the bridge crew about Galaxy missions and the missions will appear on the choice there before getting back on the tab where it is usually found. (If it doesn't do the trick just explore the galaxy and step foot in Harmonia) and wait til the choice appear in the bridge again.