Ryoma

Weapon: Raijinto (+Eff)

Assist: Reposition / flexible

Special: Noontime / Glimmer / Sol

IVs: +Spd / -Def

Passive A: Atk/Res Unity / Darting Breath / Kestrel Stance 3 / Atk/Spd Solo / flexible

Passive B: Spurn / Repel / Close Call / Wrath / Null C-Disrupt

Passive C: Pulse Smoke / Joint Drive Atk / Atk Smoke / Spd Smoke / flexible

Sacred Seal: Atk/Spd Solo / Mystic Boost / Spd/Res Solo / flexible

• Raijinto’s refine allows Ryoma to access the coveted combination of Null Follow-Up (in the weapon effect) and speed-based damage reduction from a skill such as Spurn, Repel, or Close Call. This increases his bulk significantly while rendering him immune to guaranteed enemy follow-ups and disabling effects that prevent his follow-ups, allowing him to function effectively as a tank. 
• The ideal B slot is one of Spurn, Repel, or Close Call, as Ryoma’s bulk is rather poor without the added damage reduction they provide. Spurn is arguably the best option, since the extra 5 damage on Special activation is potentially every combat on this build, and the movement effects from Repel and Close Call are generally not very useful and can even be counterproductive, depending on the mode Ryoma is used in. However, all three skills function similarly. Wrath can be used as a more budget option, but losing the damage reduction hurts his bulk massively. Null C-Disrupt could be used to allow him to counterattack units using skills such as Dazzling Staff or Firesweep effects, but Ryoma generally appreciates the damage reduction more, especially if using Mystic Boost seal. 
• Noontime is chosen to be used with some form of Special cooldown charge gain from an effect such as Darting Breath or another breath, or a support unit such as Brave Lucina, so that Ryoma can get attacked and immediately activate Noontime on the counterattack. Glimmer or Moonbow could be used instead of Noontime to boost Ryoma’s damage. If no Special cooldown charge gain effects are available, Sol can be used instead for a larger amount of healing. 
• The ideal choice of boon is +Spd, as Ryoma depends heavily on his Spd for damage reduction and follow-ups. +Atk is a decent option as well. Ryoma does not particularly want any bane, as he uses all his stats, but -Def is preferred to -Res or -HP since his base Def is higher than his Res, and damage reduction skills diminish the value of Def and Res compared to HP. 
• The choice of A slot is flexible. A Breath skill like Darting Breath may be used to accelerate Ryoma’s special activation, as described above. If this is unneeded or unavailable, Ryoma prefers options that boost his stats significantly while providing other useful effects, such as Atk/Res Unity, Kestrel Stance, or Atk/Spd Solo. 
• The choice of C slot is also flexible. Options like Joint Drive Atk and Pulse Smoke may be valuable to boost Ryoma’s damage or prevent enemy special activation, respectively. More budget options like Atk Smoke or Spd Smoke also provide a useful reduction in enemy stats after combat. 
• There are several good choices of seal as well. Mystic Boost heals 6 HP after combat while also disabling the Wrathful effect of staves, effectively causing them to do half damage against Ryoma. Atk/Spd Solo and Spd/Res Solo also provide large useful stat boosts under a fairly easy condition. Quick Riposte can be used to guarantee follow-ups against enemies that Ryoma does not have enough speed to double, so long as he is above 70% HP.

Weapon: Raijinto (+Eff)

Assist: Swap / flexible

Special: Blue Flame / Glimmer / Luna / Draconic Aura / flexible

IVs: +Atk or +Spd / -Def

Passive A: Atk/Res Unity / Atk/Spd Bond 4 / Fierce Breath / Fury 3 / flexible

Passive B: Spurn / Wrath / Repel / Close Call / Null C-Disrupt

Passive C: Time’s Pulse / Joint Drive Atk / flexible

Sacred Seal:  Quickened Pulse / Fierce Stance / Atk/Spd Bond / flexible

• Ryoma can use the strengths of Raijinto and certain skills to tank a single hit and retaliate with a powerful Special. There are many ways he can be built to accomplish this, using different Specials and different forms of Special charge gain, so many skills on this build are flexible. As Ryoma does not have particularly high Def or Res to use Bonfire or Iceberg, Blue Flame is one of his best options, boosting damage by 25 so long as he is adjacent to an ally. Draconic Aura and Luna are decent options if Blue Flame is not available, but are generally weaker; Luna provides less damage than Blue Flame unless Ryoma’s foe has at least 50 Def, and Draconic Aura is worse unless Ryoma somehow achieves 84 Atk or higher, which is perhaps not impossible but very difficult. Glimmer is a solid low-cooldown choice that is generally weaker, but requires less support from skills like Time’s Pulse or a teammate using Infantry Pulse.
• The ideal choice of boon is arguably +Atk to improve Ryoma’s damage, but +Spd is also quite good, especially if using a B slot such as Spurn that relies on Spd. -Def is arguably the best bane, as Ryoma’s Res is terrible and taking a bane may render him vulnerable to being oneshot, and points in HP are worth more than Def or Res on a build that uses damage reduction, particularly when the point is largely to survive a single hit and counter. 
• For B slot, the ideal choice is Spurn, as it increases Ryoma’s Special damage by 5 while also providing up to 40% damage reduction proportional to the difference between his Spd and his opponent’s, up to 10. Wrath is a decent substitute that provides more damage if Ryoma’s HP drops below 75%, but the lack of damage reduction renders him far more vulnerable to being taken out by high damage hits before he can counter. Repel and Close Call also provide damage reduction, but are generally worse than Spurn due to not boosting Special damage; their movement effects are generally not very useful for this kind of build. Null C-Disrupt could be useful if Ryoma needs to counter enemies using effects like Dazzling Staff or Firesweep, but it is far more situational than the other options listed.  
• The choice of A skill, C skill, and seal depends on the choice of Special and team support (such as whether Ryoma is receiving a Pulse from a teammate using a skill such as Infantry Pulse or Ostia’s Pulse). To accomplish this, he can use skills such as Time’s Pulse and Quickened Pulse to reduce his Special count to 1 before combat, or reduce it to 2 before combat while using a Special cooldown charge gain effect such as Fierce Breath or support from Brave Lucina. The combination is more important than the specific choice of skills: some possible combinations that work could be Blue Flame + Time’s Pulse + Quickened Pulse, Glimmer + Quickened Pulse, Blue Flame + Quickened Pulse + Brave Lucina support, Glimmer + Fierce Breath with no pulses, and so on. 
• Aside from Special activation, Ryoma appreciates skills that increase his Atk and survivability. Atk/Res Unity and Atk/Def Unity are great options that provide significant gains to Atk and one other stat while also effectively reversing any penalties he has in those stats. Atk/Res Unity is arguably better because of Ryoma’s low base Res, but both are quite good and have advantages over the other. Atk/Spd Unity does not exist at the time of this writing, but would likely be the ideal choice if it did. Atk/Spd Bond is also solid for similar reasons, especially if Ryoma is using a B slot that reduces damage based on his Spd like Spurn; the extra Spd can serve as extra bulk, and the penalty neutralization from Atk/Spd Bond 4 is a good check to Chills and similar effects. Fury 3 is a decent budget option that improves Ryoma’s damage, Spd, and bulk all in one. 

Weapon: Raijinto (+Eff)

Assist: Reposition / flexible

Special: Moonbow / Luna / Galeforce / flexible

IVs: +Spd or +Atk / -Def or -Res or -HP

Passive A: Flashing Blade 3 or 4 / Life and Death 3 or 4 / flexible

Passive B: Windsweep

Passive C: Time’s Pulse / Odd Tempest / Spd Smoke / Def Smoke / flexible

Sacred Seal:  Life and Death / Flashing Blade / Swift Sparrow / flexible

• Raijinto’s Null Follow-Up effect allows Ryoma to use Windsweep with no drawbacks, since the effect is always active when he initiates combat. Denying counterattacks from physical units is extremely powerful in some contexts and can make him very useful on some teams. 
• The ideal boon is +Spd to allow Ryoma to activate Windsweep and double as often as possible, but +Atk is also a good option for extra damage. Any of -Def, -Res, and -HP are fine choices for bane, since Ryoma should not be getting counterattacked unless fighting the rare enemy using Null C-Disrupt or with extremely high Spd. 
• Moonbow is generally the best Special due to its low cooldown and providing more damage against enemies with high Def. Luna is an option that adds more damage, but Ryoma requires some form of Special charge gain such as Time’s Pulse to activate it in one combat. Galeforce can allow Ryoma to act multiple times per turn, but likewise requires some outside Special charge gain for him to activate from one combat. 
• Flashing Blade is a great choice of A slot or seal, as it allows Ryoma to activate Moonbow on his second attack provided he is faster than the enemy and they are not using a Special charge-reducing effect such as Guard or Special Fighter. Flashing Blade 4 in particular provides 5 “true damage” that Ryoma will deal so long as he is faster than the foe, which is great against foes with high Def that he struggles to damage otherwise. 
• Other than this, Ryoma’s best A and S skills are those that boost his Atk and Spd such as Life and Death, Swift Sparrow, Atk/Spd Solo, or similar.  
• The choice of C slot is flexible. Time’s Pulse reduces Ryoma’s Special cooldown by 1 at the start of his turn, if its cooldown is at max. This could allow him to run a stronger special such as Luna and activate it in his first combat on a turn. Odd Tempest and Even Tempest improve Ryoma’s Mov by 1 on odd and even-numbered turns, respectively, which may allow him to reach enemies he otherwise could not. Spd Smoke and Def Smoke are solid budget options which debuff enemy units within 2 spaces of Ryoma’s foe after combat; Spd Smoke allows him to double and activate Flashing Blade and Windsweep more easily, and Def Smoke allows him to do more damage.