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While the Koubu class claims to be one class (Cavalry for Sakura and Sumire and Mage for Iris), it has a movement like an infantry wearing boots (all Sakura Wars Koubu have this special movement). Meaning they can move over things like forests much easier than normal Cavalry. In other words, they work like Infantry with built in Boots.
However, unlike Iris, who has vastly superior stats in her Koubu, Sakura's Infantry class has +28 more ATK and a whopping +105 more SKL. Remember how her talent works. If her SKL stat is higher than the enemies, she attacks first, like in a traditional RPG, before the enemy has a chance to counter. Meaning if she can kill, she won't take any damage in retaliation.
Conclusion
1. For Evil Slayer ( You should use your sakura in Evil Slayer line if you have apex boot or divine boot)
Weapons: Kervinter/balanced blade> Spirit Sword ( apply 1 debuff and remove one buff after crit attack)> Hrunting>>Dragon Slayer> other SSR sword and lance
The choice of armor and headgear are not that essential
Armor: Carbon fiber armor> Bloodline Magic Armor/ Aeolus's Battle Armor> other SSR armor
Headgear: Carbon fiber armor> Reaper Breath > Aeneas' Helmet > other SSR headgear
Accessory: APEX boot >> Divine Boot
2. When you don't have Evil Slayer, go Koubu line
Weapon, armor and headgear selections are the same with her Evil Slayer line.
Accessory: Overlord Badge> Slayer's Emblem> Winged Shin Guards>Bracer Emblem >> others
For 'CARRY Sakura'- In Empire focused box- Spirit sword> Kernviter/balanced balde
Spirit Sword with Apex Boots would be the #1 combination as her Spirit Sword offers more SKL, which allows for her to get those attack firsts in, as well as it boosts her ATK for harder-hitting attacks.
Balanced Blade/Kernviter on the other hand offers DEF/MDEF, which isn't as important to her (at all). So you're only really getting the AoE range boost from it. No damage or SKL stat boosts at all. Thus instead of taking Apex Boots, which only offers 5% ATK (and the mobility), you're better off with Slayer's Emblem or Judge Talisman for the 8% ATK and additional 12% Flier/Holy damage, depending on the one you use to help supplement the damage. Remember that AoE's already do less than single target attacks and one of those, Ouka Houshin, has a bleed that works off of her ATK stat. So by using both Balanced Blade/Kernviter AND Apex Boots, you're lowering her damage output even more.
Back to her Spirit Sword, even in an AoE focused build, the higher SKL can really help against melee attacks, possibly killing off the would be attackers before they even get to hurt her (thus causing them to be hesitant to attack with anything but ranged or AoE against her). Along with its ability to remove a buff and and apply a debuff when she does need to single target attack (say if either her skills are on cooldown or there is just one enemy, thus not wanting to waste the skill).
For supportive debuffer Sakura in an AOE focused team- Kernviter/balanced balde> Spirit sword
You need Kernviter more because it really provides the positioning benefit in higher-level PVP battles, where your sakura NEEDs to debuff the enemy healer, and she can RIP after this.
Conclusion: Spirit is the best weapon to make the best sakura, but not necessarily to make the best team. If you are using a rush strategy/ AOE strategy, sakura's debuff has much more value than her ability to deal enough damage, in this case, you may consider Kernviter. But if you are using Sakura as your carry in an Empire team, she needs to AOE, and be tanky and survive throughout a battle.
Breeze Vs Clock >>> magic > others
Breeze deals more damage than Clock. With 30% chance, Sakura usually can find a chance to initiate a battle easily. It fits better for a RUSH team.
With Clock build, it fits better for a tank-push strategy. After Sakura use her heal reverse skill-Hyakka Ryoran, enemies are forced to remove debuffs immediately. If clock is triggered, it usually result in a gg (because enemy usually could not remove heal reverse effect in consecutive turns without healing).
Hyakka Ryoran+ Ouka Houshin/Roar + Deathmatch
Zealot (in most case), Bone Dino (when countering infantry) and Heavy infantry (when countering lancer). Keep in mind even when you try to counter infantry and lancer, in most case Zealot is still your best choice if you have high training in holy/mage troop.