TV Tropes
A Child Shall Lead Them: Luckily, it's what the Senate wanted. Unluckily for them, they thought a child emperor's strings easier to pull from the shadows. How sorely mistaken they were.
Badass Adorable
Break the Cutie: By the end of the game, everyone this kid loves and cares for is dead. You see him break multiple times as a result. It doesn't help that the majority of the people who died either died protecting him or in his name.
Cain and Abel: Mostly subverted, Larsa and Vayne clearly love each other dearly but ultimately Larsa challenges his brother's authority when he feels he can no longer stay idle to his plans.
Combat Medic: You'll probably appreciate Larsa most for his healing skills, but he's a decent fighter too. His healing magic gets an upgrade in the International version.
Crutch Character: It isn't a bad idea to save the optional sidequests and bosses for Larsa's second time joining the party. Besides the fact that Guest Party members are always a good thing for the fourth swordarm, Larsa's infinite supply of Hi-Potions make a lot of the optional parts of the game much easier. Without going into too much detail on how his Gambits work-the kid throws out healing items constantly, which take effect much faster than healing spells and will probably heal more than they do. In the No Export for You International version, guest party members work differently as you can control them. This means that Larsa no longer has infinite high potions, but this is compensated by him getting very useful white magic- more powerful than you likely have at his parts of the game.
Cute Shotaro Boy
Dual Wielding: A joyeuse rapier and swordbreaker
Dude Looks Like a Lady: People to this day still think he's a she. It's the pretty red shoes. Then there's the fact that he's initially known as "Lamont," not the most gender-specific name, and he isn't explicitly referred to as a male by anyone until some time after he joins you. That, and his ears are pierced, his hair is pretty long and puberty is miles away.
Guest Star Party Member
Heroic BSOD: Has a brief one when Al-Cid reveals that his father "passed away." He officially checks himself out of the conversation at Mt. Bur-Omisace once he learns of his father's death and probably didn't hear a single word said afterward.
Hyperspace Arsenal: The kid is famous for having an infinite supply of Potions, and he uses them liberally. Subverted in the International Zodiac Job System re-release, where Guest party members use items from your inventory instead.
Imperials Who Actually Do Something: Even if this means sneaking away from several escorts and Judge Magister guards to do so.
Intergenerational Friendship: With Al-Cid. Larsa thinks Al-Cid needs to be more serious and Al-Cid thinks Larsa needs to chill out.
Item Caddy: Larsa has potions up the wazoo and you will appreciate them.
Magic Knight: In the International Zodiac Job System, he masters some Black magic spells, and knows the Shades of black technique, which allows him to cast for free random black spells.
Motor Mouth: In the Japanese version. Just... slow down, Larsa. Especially when explaining things you're not even supposed to know about.
Odd Friendship: With Penelo. Brother to the Consul of Dalmasca and fourth son to the Emperor of the enemy empire? It's okay! Not all imperials are bad.
The Red Mage: In the International Zodiac Job System, Larsa becomes one (though different from the Zodiac Job's version of the game). He loses his infinite supply of Hi-Potions, but is granted many powerful white spells before anyone else, and even some black magic spells (plus the Shades of black technique), making him a jack of all trades. Combined with his quite high Magic power, high MP pool, his ability to wield a sword and his very high evasion, he is a force to be reckoned with, though he still lacks in the HP department.
The White Prince: While he is certainly skilled in politics, especially for a twelve-year-old-boy, he is still painfully and incredibly naive.
Tsundere: Specifically toward Al-Cid.
Wise Beyond Their Years: He's only twelve, but is very intelligent and well-spoken, and manages to play a few rounds of Xanatos Speed Chess against his older brother.
Xanatos Speed Chess: This kid is determined to bring about peace and end the war before it consumes Ivalice, but knows full well he can't bring it about alone. Cue him going to the people who can stop the war. Even as Vayne picks those people off one by one either by killing or manipulating them, Larsa is quick to revise his plans.
Youngest Child Wins: Toward Vayne.