|This build is primarily to make a Shiro a good physical tank for the front lines in a battle by trying to enhance his defense stat as much as possible. With Bright Naginata that gives +4 atk/def when attacked, with +def ivs, steady stance, close defense, and summoner support to top it off, that leads shire with near, if not, over 50 def to survive physical attacks on enemy phase.
For the assist, swap would be good to get someone in and then back out of a danger area in a battle or to avoid mages as Shiro's res isn't exactly the best. The special should be either Ignis or Bonfire to give a flat rate of damage that is enhanced by Shiro's boosted defense stat. The A skill should be either Steady stance or Def+3 (as budget[comment:he comes with steady stance 3...]) to increase Shiro's defense. The B skill is either vantage or Quick Reposte to be able to land an attack in case if anyone pierces through Shiro's def and knocks down his hp a bit too low so he can instantly fight back after taking a few drops in his hp. C slot selections are Def Tactic (His default skill) or Threaten atk to make allies slightly tanker or enemies weaker in case if allies such as mages, that can't handle physical attackers, can get a slight boost in stats that may allow them to survive. Seals could be either Close Def or Deflect Melee to emphasize Shiro to be pure Defensive Tank.