Soujuurou has four basic use cases: as a farming, a one-shot blaster, an atypical fastplay frontliner, and an anchor. I’ll go through each one by one.
For farming, Soujuurou functions like Arash, Chen, and Habetrot, with the caveat that his role is taking out single enemies rather than whole waves. This makes him less useful for lower-level farming, but much more fit for 90+ and 90++ nodes. He’s most useful for Arts teams, as a single Castoria Charisma provides him with enough external charge to NP, assuming he has Mana Loading maxed. The Buster and Quick supports unfortunately do not provide the partywide charge Soujuurou needs—but if you can afford to give him charge, either from a CE or from a spare battery, you can use him anywhere. If the first wave of a node is a single enemy within Soujuurou’s damage range (which is around 100k with a single Castoria Charisma, or 135k with the Berserker class score maxed—and yes, Class Score does make a deceptively big difference and is very much worth the resources) he can clear it on his own, ensuring the primary DPS only has to NP twice. More commonly, though, Soujuurou is useful for effectively increasing your damage output against a single target, when an AoE Servant is already using their NP. High-end farming nodes often feature a first wave with one or two weak enemies and one strong one, which can be a challenge for Servants who are reliant on ramp and the like for their damage output. Soujuurou solves that problem—you can place his NP after your primary damage-dealer’s to finish off the stronger enemy.
Typically, for Soujuurou farming, you’ll want Soujuurou/DPS/Castoria/Oberon/Castoria. The Servant ordering does matter, as you want to be sure the support who comes in to replace Soujuurou is the last one you want on the field. On turn 1, you use all of the first Castoria’s skills on your DPS, and then you plug her out for the second, using her skills as needed. You let your DPS and Soujuurou both NP on turn 1, and then turns 2 and 3 proceed as normal. You can also do similar things for Quick and Buster, but that generally requires a starting charge CE on Soujuurou, which can be a farming efficiency loss if your event drop CE doesn’t provide starting charge. Soujuurou does very much appreciate Summer Skadi’s charisma, though, so if you can provide him with starting charge, he’ll do a fair bit more damage in an ideal Quick team than in an Arts one.
The one major drawback to using Soujuurou to supplement farming (aside from time) is that you can’t afford to run a full set of 5* CEs if you’re also running Soujuurou, three SSR supports, and an SSR DPS, which can result in a drop in farming efficiency in some situations.
Soujuurou’s second use-case is as a one-shot blaster for harder fights. His role here is similar to his role in farming—to provide extra damage early in a fight, with minimal loss to tempo. You can use essentially the same setups as above, but since you aren’t worried about CE efficiency, you can freely give Soujuurou a starting charge CE that also pushes damage, which means he’s no longer quite so Arts-locked (although in an Arts team he can run something like the Black Grail for even more damage).
As a slight variation on this, you can start with the DPS not on the field and have Soujuurou immediately NP with as many of your supports’ buffs as you can afford to spare. This can be particularly nice for four-break-bar fights. Typically, if you’re fighting something with four break bars, the first bar doesn’t have that much health, which means even with just a good CE and maybe a buff or two, Soujuurou stands a good chance of being able to break the bar himself—especially if you’re willing to reset for a Buster card or two to start the fight with. This gets even better if you can wait till turn 2 to have Soujuurou start blasting, since you can use Soujuurou’s third skill to further boost his damage and hopefully get you extra Buster cards… though you may start to run into survivability issues for your supports at that point, as they’re taking two turns’ worth of potential hits before your DPS comes in. At any rate, the general idea is that once Soujuurou NPs and breaks a bar, he removes himself, and then you’re left with three break bars and a fresh DPSs—a perfect setup to break a bar each turn and win the fight quickly.
Alternatively—and especially if you aren’t aiming for min-turns—you can stick Soujuurou in the fourth or fifth team slot, knowing that you can rely on him for damage later in a fight without needing any particular assistance. He’s still a one-and-done damage-dealer in this case, but instead of breaking open the start of a fight, he shows up after your initial damage output is done and a Servant or two dies, and his self-sufficient kit helps you keep the momentum going to hopefully close out the fight effectively.
Soujuurou’s third use case is the most complicated of them: as a proper frontliner. It’s unintuitive to take a Servant with a self-sacrifice NP and build a whole team around them, but Soujuurou has several things going for him. Most important is his first skill: even if he’s at very low HP (which he will be almost always in this setup), he’s unlikely to go down unless you get very unlucky. The general idea is that you supply Soujuurou with a guts buff so he can use his NP without dying, and then you rely on Buster crits otherwise. You typically won’t get three NPs this way, since that requires two separate guts sources, and there aren’t any guts options that don’t imply losing a source of NP charge somewhere.
Strategizing around two NP uses instead of three substantially opens up your team-comp flexibility. My best advice here is to get creative—you’ll have the best time with DPS Soujuurou by trying different setups and seeing what works best for you. That said, there are three main ways you can get a guts on Soujuurou (CE, Mystic Code, and support Servant), so I’ll provide an example team that relies on each of those options. Each of these teams will follow the same general game plan: an NP turn, followed by a buster crit turn, followed by another NP turn.
If Soujuurou has a guts CE, you can afford to run supports that provide maximum damage push. For this particular setup, we’ll do Koyan/Soujuurou/Chen Gong/Merlin/Koyan, with Kaleid on Chen and a guts CE on Soujuurou. Notably, this setup does not rely on Chen Gong getting himself killed, as we want his third skill for damage push and fishing for a Chen death introduces extra RNG even beyond drawing cards at the right times. On turn 1, you use Soujuurou’s first and third skills (picking Buster for skill 3), along with all skills from both Koyans, plugging out one Koyan for the other. You also use Chen’s taunt on Soujuurou, which both gets Souujuurou some extra defensive NP gain, just in case, and protects Chen from dying before you’re done with him. You have Chen and Soujuurou NP (in that order, unless there’s more than one enemy), which kills Koyan and brings Merlin in. In the worst case where Soujuurou drew no usable cards and didn’t get attacked on turn 1 (which is unlikely given Chen’s taunt), he’ll have no NP gauge on turn 2. You then use Chen and Merlin’s AoE charges to bring Soujuurou to 30% gauge, at which point Soujuurou uses his second skill, bumping himself to 60%. This also gives him 100% crit damage up, as he should be at nearly no health due to using his own NP. Merlin’s and Chen’s third skills each provide 50% Buster up and 100% crit damage up, giving Soujuurou truly absurd Buster crits. If he drew at least two cards, he’ll automatically get the 40% charge he would need to loop in the aforementioned worst case—gaining 10% charge per Buster per Koyan—but even if he doesn’t, there’s a good chance the defensive NP gain from Chen’s taunt has already closed the distance. On turn 3, Soujuurou NPs again, hopefully winning the fight, and making way for a secondary DPS if not.
If your guts is coming from your Mystic Code, you naturally can’t run as many supports. For variety, we’ll use Crane instead of Chen. Specifically, for this setup, we’ll go with Crane/Soujuurou/Koyan/Koyan. Again, the order matters—Crane and Soujuurou have to be positioned such that Crane’s buffs go to Soujuurou, and the second Koyan must be in the fourth slot in order to come in after Crane. Here, Soujuurou needs a 50% starting charge CE. Like the above setup, on turn 1, you use both Soujuurou skills, along with all skills from Koyan and Crane. You use Crane’s NP before Soujuurou’s rather than after—he doesn’t need the extra NP charge, and he appreciates the extra damage. Crane leaves and brings Koyan in. Koyan uses all of her skills on Soujuurou, who then uses his second skill, bringing him to 100% charge and giving him 100% crit damage up. Ideally he then has three Buster cards for a BBB chain, and then on turn 3 he NPs again and dies. This setup will likely result in less overall damage than the one above, but it has two key advantages. For one, the loop is entirely RNG-independent, so if Soujuurou is never attacked and draws no cards on turns 1 and 2, he still gets his NP on turn 3. This case is still probably a reset (in addition to being exceedingly unlucky) as it means you’re doing basically no damage on turn 2. In fact, if this happens, you’re probably better off NP-ing on turn 2 rather than turn 3, since Soujuurou has as many buffs at that point as he will on turn 3, and that gets him out of the way faster for your other damage-dealer to do cleanup. The second advantage of this setup is that it leaves two Servant slots open rather than one, so you can bring a support for your backup damage-dealer, or two backup damage-dealers instead of one, which can make it somewhat better for fights where Soujuurou can’t reliably clear the whole thing on his own.
If you’re looking for a guts from a support, meanwhile, you have specific implications for your team setup. I’ll go with Santa Nightingale as the guts provider, since she’s free and permanently available. You can run a double Koyan setup that is essentially the same as the above, replacing Crane with plug Night—but we can be more creative than that. In the interest of not just recreating the same team, we’ll do something somewhat weirder: double Oberon, with the Black Grail. This is, to be clear, somewhat impractical and probably not optimal, but the idea behind the setup to follow is to demonstrate the types of creative teams you could create if you were so inclined.
For this third setup, you run Santa Night/Soujuurou/Oberon/Oberon. On turn 1, you use all of the Night skills and then plug her out for the second Oberon. You use both Oberons’ NP damage buffs, along with a 50% charge from one Oberon, after which Soujuurou NPs. In order for this to work, Soujuurou needs Mana Loading (though it doesn’t need to be leveled), as he only gets 90% charge on turn 1. He also needs a healing command code on at least one of his cards, and he needs to draw that card on turn 1 or turn 2, or you need to be using specifically the newer plugsuit, which has a healing skill—Night’s guts revives Soujuurou with 1000 HP, and BG deals 500 damage per turn, meaning it will kill him on turn 2 if he receives no healing. On turn 2, you use the other Oberon’s 50% battery, which you then double via Soujuurou’s battery. The Oberon battery also gives you stars to help Soujuurou crit. Soujuurou does need to gain at least 20% extra NP gauge somewhere in this process (most likely through defensive NP gain) as Oberon’s battery’s demerit will drain 20% charge from Soujuurou before the next turn. Assuming he does get the extra charge he needs, though, on turn 3 you use End of the Dream from both Oberons, at which point the many NP damage buffs you have are all doubled (though only once, sadly), and you also have several Buster buffs in play. This setup has much lower crit damage than the others, but in exchange your final NP will hit much much harder.
Again, these are just examples. There’s a lot of flexibility with how you build teams around Soujuurou, and if you’re inclined to do so, you’ll want to experiment with the tools in your box to see what works best for you. The hypothetical teams I listed all assume access to various top-end supports, but Soujuurou should still do pretty well even with lower-end supportive options, provided they offer a good mix of charge, crit-enabling, and damage ampage.
Soujuurou’s final use case is by far the simplest: as an anchor. If Soujuurou is alone on the field, he dodges lethal attacks and whacks things for three or four turns, closing out a fight. His third skill gives him a BBB turn, and he can freely use BAB or QAB chains otherwise. Note that he cannot NP in this setup unless you give him a guts, even if that NP would kill the enemy, as you automatically lose the fight if all of your Servants are dead, even if the enemies are also dead. This is easy to solve, though—a guts CE on Soujuurou provides a get-out-of-jail-free card of sorts, letting him NP once without it losing you the fight. You can also look at a guts CE as giving you the ability to trade an extra turn of survival for a turn of increased damage, which lets you respond more flexibly to the situation you’re faced with at the end of a fight.
I’ve addressed CE options for Soujuurou pretty thoroughly above, but in short, the options are charge (for self-sufficiency and quick kills), damage boosts (for hitting harder while Soujuurou is on the field), and guts CEs (for using Soujuurou’s NP without him dying). I’d also like to call attention to one other option: GudaGuda Poster Girl. Soujuurou is a great candidate for that specific CE, as it provides a huge damage buff in a bracket Soujuurou has little of otherwise. The buff only lasts for three turns, but Soujuurou doesn’t usually want to be around for more than three turns anyway. Even better, it turns Soujuurou’s innate bulk into party defensive utility, as you can count on Soujuurou to safely eat enemy hits for the duration of Poster Girl’s taunt. If you happen to have that CE, it’s a great pick.
Crit CCs are Soujuurou’s best friend. If you’re not using Koyan, Soujuurou doesn’t have a great way of drawing stars to himself, which means he needs a lot of stars on the field in order to crit reliably. Star gen CCs help with this. Alternatively, if you are mostly using Koyan, crit damage CCs let Soujuurou hit harder—although the bonuses they provide are pretty small relative to the other buffs Soujuurou should be getting. Finally, there’s a very small case to be made for healing and burn/curse/poison-removal CCs, only because they can help Soujuurou offset damage-over-time debuffs (or The Black Grail’s demerit in the case of healing), which are one of the few things that can kill him through his first-skill’s dodge.