Alvin's arte list foreshadows a lot about his character. For starters, Alvin is the only character in the game who has no Spirit Artes at all, which foreshadows the fact that he's from Elympios. His arte list starts off with traditional Tales hero attacks like Tiger Blade and Demon Fang; but he gains artes like Dragon Swarm, which hint at his Anti-Hero and Chronic Backstabbing Disorder traits. Lastly, most of his artes are Fire-based, which counters Presa's water element, hinting at a connection.
Earlier on, his pool of Link Artes with other characters is much smaller than everyone else, which foreshadows his untrustworthy nature.
The way Teepo acts, including its obsession with Milla's breasts, despite the fact that it's only a reflection of Elize's inner thoughts. Teepo acts that way because Elize views it as male, and thus unconsciously makes it act in a stereotypically male fashion.
When Milla losses The Four early in the game, she's no different from any other human. It seems as if the only thing that separates the Lord of Spirits from a puny human is control of The Four. This is because she really isn't any different from other humans. The Four told her she's Maxwell and so she believes it.
In Fort Gandala, Rowen attempts to use an arte to unlock the door and break the hex chains on the prisoners legs. Yet he needs the others help - Jude, Alvin, Elize and Driselle. Yet with five people working together, they struggle to gather enough mana until Teepo wakes up. This is because Alvin is from Elympios, and has no mana lobe - and thus despite pretending, he cannot help with the spell at all.
And of course, the reason why Teepo waking up is so helpful is that Teepo is a booster, meaning it would be able to increase Elize's mana output and make enough to save the day.
Also even with Alvin not being able to produce mana, Jude, Elize, Rowen, and Driselle should of been able to stablize is it at least but still couldn't. Because Jude's dad is from Elympios, thus Jude has a smaller Mana Lobe meaning he isn't contributing as much mana as the others!
Presa's story. Towards the end of the game you find out that she used to be in a relationship with Alvin and was a spy who formed relationships with high ranking military officers. Alvin betrayed her and she was caught (although it's possible he didn't know about the spying). She doesn't elaborate but says she went through some terrible experiences as a result of this. Considering how female spies, especially those who used sexuality, have often been treated, this gives rise to some nasty implications.