Ronin are a physical damage dealer class. Unlike Landsknechts, though, that is all they do. They have the highest STR of any of the classes, katanas have high ATK value, you can probably infer how their job usually goes down based on those. The tradeoff for this is that they're the most fragile front-row class; their HP and VIT are low, especially compared to other front row classes. Compared to EO2U, though, Ronin are actually a very effective damage dealer class, because their skill damage numbers are either on par or higher than other classes' skills on average, and the difference between their STR and the next-highest STR stat (Highlander) is actually fairly appreciable, instead of just literally one point.


Stats

(Full stat table)

Common Passives: ATK Up, HP Up, TP Up
Gathering Skill: Mining

As mentioned in the opening paragraph, Ronin have low HP and VIT, making them very fragile as-is, especially given that they're designed for the front row. Their TP, TEC and LUC are also very low (in fact, their TP and LUC are the worst of any of the classes). On the other hand, their STR is extremely high (highest of all the classes, again), and their AGI's very good (although it's offset a bit by accuracy penalties and katanas imposing speed penalties).


Katana Mastery


Required to learn katana skills. Increases damage dealt with katanas.

Slantwise Cut


Deals melee STR-based cut damage to one enemy. Allows the user to use any skill that requires a stance on the next turn, for one turn. Has no speed modifier and a base accuracy of 98% at all levels.
Slantwise Cut's mostly designed for random encounters; deal some damage on the first turn, and then follow up with Flame Grater or what have you on the next turn. Once you have all the proper attack skills you want maxed out, maxing out Slantwise Cut isn't the worst idea.
This tends to not be an amazing skill by itself, but it's slightly more economic than setting up for a stance in a fight you know will not take much time to finish.

Perfect Chaser


For one turn, the user will chase all normal attacks by other party members. Each time Perfect Chaser activates, the chance of it activating again on that turn is reduced. Initial prep has priority, chase hits have a base accuracy of 98% at all levels.
Chase normal attacks. Bulergh.

I'm having to come up with new onomatopeia for disgust.
It can't set off chaser effects, and it isn't set off by other chasers. It's not worth using.

Upper Stance


Places a buff on the user that enables Upper Stance skills and increases the user's physical attack and physical defense for a set amount of turns. Has a 200% speed modifier at all levels.
Upper Stance is the damage stance, so to say, and it's therefore probably the one you are going to immediately go for.
Ronin's got a massive issue where they have one branch that does a lot of damage, and two other branches that don't do as much damage as that one. As a damage dealing class, this is fairly damning for the other two.

Horse Slash


Requires Upper Stance to use. Deals melee STR-based cut damage to one enemy. Has no speed modifier and a base accuracy of 98% at all levels.
Horse Slash deals a pretty good amount of damage relative to how much TP it costs. It'll serve you up until the midgame or so. After that point, though it's probably time to put points in Swallow Strike.
This is your bread and butter as Ronin for most of the early parts of the game. It's also useful later on for cleaning up smaller enemies to save a bit of TP.

Flame Grater


Requires Upper Stance to use. Deals melee STR-based cut+fire damage to one row of enemies. Has no speed modifier and a base accuracy of 98% at all levels.
Gives the Upper Stance tree some encounter-clearing capability. Yeah, you need Upper Stance to use it, but in random encounters you can usually just go Slantwise Cut -> Flame Grater, and you should be good. By that point, Flame Grater will probably kill whatever enemies you were targeting, since they should be at low HP from the previous turn.
Once you actually open the ability to use the skill against enemies, it's great. The two-turn economy kinda hurts it in comparison to the other area of effect competition in the game, though.

Swallow Strike


Requires Upper Stance to use. Deals multiple instances of STR-based cut damage to one enemy. Has no speed modifier at all levels.
Swallow Strike is, for all intents and purposes, the best Ronin damage skill--hampered a little by its base accuracy at basically every level before 10, yes, but still the best nonetheless. If you're really, really worried about it missing, just toss an accuracy buff on your Ronin or bind the target's legs. Enemies tend to be more vulnerable to leg binds than the other two, so it's not like it'll be that hard.
This is easily one of the strongest non-conditional single target attacks in the game. It takes a while for it to get going due to TP costs and SP investment, but once it does there's not much that it can't tear into effectively.

Clear Stance


Places a buff on the user that enables Clear Stance skills and increases the user's physical attack and physical defense for a set amount of turns. Has a 200% speed modifier at all levels.
I'll just say it straight-out: The Clear Stance tree is complete garbage. One of its skills isn't an attack skill at all, its multi-target coverage is limited to row-piercing, and its "big" skill is complete garbage.
What the hell happened with this branch? Drawing Stance has at least some amount of performance ability, but this just feels like leftovers. Some of the worst skills in the game for a damage class, if not the worst.
Razor Dodge


Requires Clear Stance to use. The user will dodge attacks directed at them for one turn. Each time Razor Dodge activates, the chance of it activating again on that turn is decreased. Razor Dodge has a maximum amount of times it can activate per turn. Has priority at all levels.
Why is this on a damage dealer class?
This would be good on a Provoked Protector if it didn't require you to set up a stance beforehand.
Lightning Stab


Requires Clear Stance to use. Deals melee STR-based stab+volt damage that pierces enemy rows. Has no speed modifier and a base accuracy of 98% at all levels.
Row-piercing for multi-target coverage are you kidding me
Well, uh... the damage modifier isn't that bad for a piercing attack? I guess? Volt's not a very high-coverage element in EOU...

Arm Strike


Deals melee STR-based cut damage to one enemy. Attempts to bind the target's arms. Has no speed modifier and a base accuracy of 98% at all levels.
Bleh damage (actually less than Lightning Stab, for crying out loud), and good luck ever binding anything due to garbage Ronin TEC and LUC.
This is supposed to be this branch's big skill, huh? The base infliction rate is pretty high, I guess? That damage is just pitiful, though.
Drawing Stance


Places a buff on the user that enables Drawing Stance skills and increases the user's speed, accuracy, and evasion for a set amount of turns. Has a 200% speed modifier at all levels.
This is easily the lesser of the two good stances. On top of that, Drawing Stance doesn't provide an attack buff or a defense buff. It'll definitely make your Ronin fast as hell, though.

Beheading Cut


Requires Drawing Stance to use. Deals melee STR-based cut damage to one enemy. Attempts to instantly kill the target. Has no speed modifier and a base accuracy of 98% at all levels.
On the one hand, good luck ever proccing that with Ronin TEC and LUC. Also on the one hand, Beheading Cut deals garbage damage. On the other hand, it's one of two innate player skills that inflicts instant death.
You use this to get gloves for your Landsknecht. You also use this to feel miserable in the early game because you do miserable damage. It's cheap, I guess.

Frigid Slash


Requires Drawing Stance to use. Deals ranged STR-based cut+ice damage to all enemies. Has no speed modifier and a base accuracy of 98% at all levels.
The fact that Frigid Slash is ranged means it's actually really, really good for clearing out random encounters. If you're going for a Upper Stance build, you could do worse than putting enough points into Drawing Stance and Beheading Cut to unlock Frigid Slash, and use that alongside Slantwise Cut for random encounters.
This is actually pretty good. Unconditional all-targeting elemental damage is pretty damn effective against a lot of random encounters, especially ones with physically resistant frontliners keeping you from the dangerous backliners.

Charging Slash


Deals melee STR-based stab damage to one enemy. Has no speed modifier and a base accuracy of 98% at all levels.
Charging Slash is thoroughly mediocre. I really do not have a ton to say about it.
The main thing this has going for it is the lack of an accuracy penalty, but Swallow Strike eventually overcomes that for the most part anyways, so...

Peerless Stance


Requires any of the stances to use. Places a buff on the user that lets them use all katana skills, regardless of what stance they require. Also increases the user's physical attack, physical defense, speed, accuracy, and evasion. Stacks with the buffing effects of the normal stances, apparently, but I dont' know how that works. Lasts for 4 turns at all levels. Has a 200% speed modifier at all levels.
Peerless Stance is something you use once the duration of your first stance is about to run out. In effect, it's not gonna be that much of a difference, but it's still soemthing you'll want by endgame.
I don't have much to say here. It's good for extended encounters and generally just makes your Ronin better when it's up.

Crit Up


Increases the user's critical hit rate.
lol
This doesn't work with chasers so it's pretty worthless.

Severing Slash


At the start of the battle, may activate and attempt to instantly kill all enemies.
There's a specific formula for how Severing Slash activates, but I don't feel like pasting it, because Severing Slash is a waste of skill points, and after a certain point in the 6th Stratum, it becomes actively dangerous to have around, because certain enemies do not react well to having dead allies, and are immune to instant death themselves.
This can be useful for some parts of the game if you're lucky, I guess? It's also amazing at pissing off crustaceans and eats up SP that could go elsewhere.

Breath


Restores HP for all party members in the user's row.
lol why are you having your ronin heal
This could be used for row swapping shenanigans with a support on a Grimoire Stone, but at that point you're forgoing more useful utilities for the sake of a gimmick.

Indomitable Cry


Attempts to inflict fear on all enemies. Has an 80% speed modifier at all levels.
A garbage base chance hampered even further by terrible Ronin TEC and LUC. Avoid.
You need a Hexer to get the most out of fear, and they're better at inflicting it anyways.