Swordman

The swordsman is a Rank D, or beginner level, frontline fighter that can deal heavy damage to a single enemy. The swordsman's starting magic, Flame Sword, deals damage and debuffs the target's vitality to lower its maximum hit points.

Official Description
Swordsmen are the only character who can use a shield. And their high defense and HP set them apart.

Do you want to protect your team from the enemy's attack? Swordsmen can serve as a powerful shield that protects your mercenaries.

However, they have weak attack power for a melee fighter and can only strike one enemy at a time.

Attack Type
The swordsman can hit any front line target that is not flying. Despite the official description, the swordsman seems to produce high damage attacks.

Flame Sword is a magic attack that deals damage and reduces the target's vitality. The result should be an enemy that cannot regain its original full hit points for the duration of the spell. Flame Sword lasts one turn and requires two turns before it can be used again, so it is impossible to keep an enemy's vitality debuffed with just one swordsman.

Other spells the swordsman can learn include Guard Dispel, Deadly Strike, Dark Seed, and Break Down. Guard Dispel removes the Holy Guard buff from the first row of the enemy squad. Deadly Strike allows a swordsman near death to trade a super powerful attack in this round for his turn the next round. Dark Seed causes damage over time and can combine with Hex of Darkness to create the Hell Flame combo attack. Break Down damages all enemies with an earthquake. If cast on an enemy effected by Chaos Wind, Break Down triggers the Destructive Wind combo attack.

Attributes and Upgrades
The swordsman starts with the highest strength (STR), dexterity (DEX) and defense (DEF) of all Rank D ranged fighters. Players can upgrade him at level 20, 50, 80, and 100 with Ashen Cyrstals. As he progresses, the swordsman will continue to have the highest STR and DEF among his rank D ranged peers, but the spearman has only slightly lower attributes while possessing the ability to damage two enemies in a column. Additionally, players may find that spears add more damage than swords.

The high DEF and vitality (VIT) of the swordsman makes him the ideal front row fighter. He can soak up hits with his high defense and hit points to keep your frail rear units safe.
Statistics (not including equipment or Growth Vials)

The Flame Sword spell hits an enemy hard and drains its vitality.

Strategy
The choice to hire a swordsman is a decision to create a "tank" on the front row to take damage for the squad. Their high DEF and HP mitigate a lot of damage that could cripple your party, but be prepared to heal them when they get hit by magic as they rank in the bottom three in magic defense (MAG DEF) among rank D mercenaries.

Choosing sword as your class for your main character ensures that your leader will have high HP and a good chance to survive. It also means your leader will likely be on the front row where he will get hit often. The benefit of being a swordsman seems to even out with the deficit.

Having more than one swordsman in a squad provides a firm front defense but lowers the damage capabilities of the squad overall as other front line fighters can damage more foes or hit harder. The key to overcoming the lower damage output of single attacks with more than one swordsman is to learn to trigger combo attacks by using the right skills.

As Rank C units become available, the player gains access to lady knights, the next tier of tanks. Lady knights outshine swordsmen in every attribute, so they make fine upgrades. The lady knight also sports better magic attacks than the swordsman, meaning that a swordsman upgraded to sword warrior might be better than a base lady knight in attributes until you upgrade her, but the lady knight is the clear choice overall.

Credits: Ralsu from TenTonHammer