Guide
How the kit works
Start Yoimiya's field time with Niwabi Fire-Dance. It converts the arrows from her Normal Attacks into Blazing Arrows, increases their DMG and makes them deal Pyro DMG. The effect ends if she leaves the field, so stay on her and shoot.
Firework Flare-Up (NA) has a chain of up to five Normal Attacks. Hitting with those shots during the Skill also gives Yoimiya 2% Pyro DMG Bonus per stack, up to 10 stacks. Each stack lasts 3 seconds, so keep attacking to maintain the bonus.
When you are ready to switch, use Ryuukin Saxifrage. It deals AoE Pyro DMG and applies Aurous Blaze to one enemy hit. Another party member's attack, Skill or Burst can trigger an AoE Pyro explosion on that enemy once every 2 seconds. If the marked enemy is defeated, the mark can pass to a nearby opponent for its remaining duration.
The Burst also gives nearby teammates 10% ATK for 15 seconds, plus 1% for each Pyro DMG Bonus stack Yoimiya has when she casts it. Outside her Skill, a fully charged Aimed Shot can release up to three homing Kindling Arrows. During the Skill, it cannot generate them.
Build and why
Use four pieces of Shimenawa's Reminiscence for a Normal Attack build. Its two-piece effect gives 18% ATK. If Yoimiya has at least 15 Energy when she casts her Skill, the four-piece effect consumes 15 Energy and increases Normal, Charged and Plunging Attack DMG by 50% for 10 seconds. Check her Energy before casting if you want the bonus.
Four pieces of Echoes of an Offering are another option. Normal Attack hits have a 36% chance to trigger a bonus equal to 70% of ATK. When a hit fails to trigger it, the chance increases by 20% for the next attempt. For reaction teams, consider Crimson Witch of Flames: its four-piece effect increases Vaporize and Melt DMG by 15%, while its two-piece effect gives 15% Pyro DMG Bonus.
Choose ATK Percentage or Elemental Mastery on the sands, Pyro DMG Bonus on the goblet, and CRIT Rate or CRIT DMG on the circlet. Elemental Mastery is worth considering when Yoimiya triggers reactions; ATK Percentage is a direct option for her attacks. For substats, look for CRIT Rate and CRIT DMG first, followed by ATK Percentage, Elemental Mastery and Energy Recharge.
Thundering Pulse is the first weapon choice. It gives 20% ATK and increases Normal Attack DMG by 12%, 24% or 40% at one, two or three Thunder Emblem stacks. Yoimiya gains stacks from Normal Attack DMG, casting her Skill and having less than full Energy; the last stack disappears when her Energy is full.
Aqua Simulacra is another option: it increases the wielder's DMG by 20% when opponents are nearby. Slingshot is a lower-rarity choice that increases Normal or Charged Attack DMG by 36% if the arrow hits within 0.3 seconds. If it takes longer, the weapon instead decreases that DMG by 10%.
Leveling priority
A sensible leveling order is Firework Flare-Up (NA), then Niwabi Fire-Dance, then Ryuukin Saxifrage. The Normal Attack is first because those are the shots Yoimiya repeatedly fires during her Skill. Level the Skill next to improve the ability that powers that field time, then the Burst for its damage.
For maximum ascension, collect 420,000 Mora, 168 Naku Weed, 1 Agnidus Agate Sliver, 9 Agnidus Agate Fragment, 9 Agnidus Agate Chunk, 6 Agnidus Agate Gemstone, 18 Divining Scroll, 30 Sealed Scroll, 36 Forbidden Curse Scroll and 46 Smoldering Pearl.
To take all three talents to maximum, the listed total is 4,957,500 Mora, 3 Crown of Insight, 9 Teachings of Transience, 63 Guide to Transience, 114 Philosophies of Transience, 18 Divining Scroll, 66 Sealed Scroll, 93 Forbidden Curse Scroll and 18 Dragon Lord's Crown.
Constellations worth it
A Procession of Bonfires is the standout upgrade here. When Yoimiya's Pyro DMG scores a critical hit, she gains 25% Pyro DMG Bonus for 6 seconds. It can also trigger while she is off-field.
If you are considering later constellations, Naganohara Meteor Swarm adds a 50% chance for each Normal Attack during her Skill to fire an extra Blazing Arrow. That arrow deals 60% of the original DMG and counts as Normal Attack DMG. Trickster's Flare is also worth considering because it adds three levels to her Skill.
You can stop at C2 or C3 rather than continue to Pyrotechnic Professional and A Summer Festival's Eve. C4 reduces the Skill cooldown by 1.2 seconds when Yoimiya's Aurous Blaze triggers an explosion, while C5 adds three Burst levels. Both lie on the way to C6, so you cannot skip them if you choose to reach it.
Teams
Yoimiya wants teammates who can contribute while she shoots, plus protection or healing to help her stay on the field. Yelan and Xingqiu are Hydro options with off-field roles. Xingqiu is also a healing option; their Hydro element gives you a route to Vaporize teams.
For protection, consider Zhongli or Citlali as shield options. Citlali brings Cryo, giving the team an element to use alongside Pyro for Melt. Furina is another Hydro option with an off-field role and healing.
For an Overloaded team, Fischl brings Electro and an off-field role, while Chevreuse brings Pyro and healing. Kaedehara Kazuha is an Anemo option for Swirl. Whichever team you choose, the ATK bonus from Yoimiya's Burst goes to nearby teammates rather than Yoimiya herself, and their hits can trigger her mark.
Common mistakes
Do not switch Yoimiya out immediately after using her Skill. Its Pyro conversion ends when she leaves the field, so you would lose the effect before using her Normal Attacks.
Do not expect Yoimiya's own hits to trigger her Burst's mark. Another party member has to hit the marked opponent. Cast the Burst when you can make use of both the mark and the teammate ATK bonus.
With Shimenawa's Reminiscence, casting the Skill below 15 Energy will not activate the four-piece attack bonus. The set also consumes Energy when it does activate, so account for that when deciding whether to use the Burst first. With Slingshot, watch the distance: an arrow that takes longer than 0.3 seconds to hit loses DMG instead of gaining it.
