I am going to highlight what would be considered spoiler for the game's plot, since not everyone here played the game, no?

♤ Despite his young age, he has absurdly strong tolerance for alcohols.
♤ Loves chocobos so much it's hilariously awesome.
♤ He's hypermetropia and he use glasses when he read something. Semi-confirmed on the ending. Kinda.
♤ He reads classic literature and history books. Not as much as chocobo coloring book, though.
♤ Dude could actually eat a lot. By that, I mean a lot. Still, his body stayed ideal. Being designed by someone who thinks pretty highly of a bishounen really is to his advantage.
♤ For the love of Harvest Goddess, don't challenge him into a game of Poker. He have amazing luck when it comes to card, or anything related to it.
♤ It's not that he's not tech-savvy. It's just that he prefers the ol' fashioned way. Sending letters > Texting. What is technology.
♤ Too mature for his age, yet too childish for his age as well. Feel free to make something out of it.
♤ Makes a pretty cute girl if he crossdress. Not that he actually would.
♤ And he's oblivious to his 'beauty'. So if someone thinks of him as pretty… He will stare at them in disbelief.
♤ Despite how often he sweet-talks to others, he's... again, dense as fuck. What are feelings, what is flirting, he has the romantic sense of a dead brick.
♤ Labelled as #1 of the team, he's the first one that was recruited into the class.
♤ He couldn't actually take care of himself all that much. His room is actually pretty messy, despite everyone's opinion on him being an elegant motherfucker.
♤ Seriously, aside of fighting, cards, and chocobos, Ace is basically a walking stone. How does he hobby?
♤ He has no actual preferences of clothing. He's pretty comfortable with anything. If any, anything that looks terribly and plainly simple is his favorite.
♤ He's actually pretty afraid of failing his part as a leader of his group. Sad thing is, he doesn't even confide it to anyone else in particular. Boku no tomodachi ga sukunai. So much.
♤ Why is he so short? Alas, his height is not exactly the best topic to converse on with him.
♤ You have just activated my trap card.