Esper Zero (Protagonist) Complete Build Guide: Free S-Tier MC, Gender Switch, Free Day Off Signature Arc, Instant Cycle Charger

Key takeaway: Esper Zero / The Appraiser is the S-tier protagonist gifted for free at 1.0 launch, with the Cosmos element, Solid Arc type, voiced by Yuma Uchida (male) + Maaya Uchida (female) — real-life siblings cast together, and is the sole survivor of the seventh-tier Hypervortex (amnesiac, able to sense Anomaly cores / Nexus). Core mechanic: Skill Cycle Rate = 100, the only character in the game who instantly charges elemental reactions. His signature Arc “Day Off” is completely free (the Eclipse hidden side quest), and he has an exclusive gender-switch feature (unlocked via In the Reflection). Strongly do not buy the limited Doomrain — save your resources for the other limited characters.

Yiboen Antique Shop appraiser, amnesiac Hypervortex survivor, real-life siblings cast together, free gender switching — Esper Zero is the S-tier protagonist gifted for free at 1.0 launch, called by the whole community “one of the most worthwhile free launch protagonists ever,” the “instant-cycle-charging machine,” and “the indispensable loop-trigger of the Synthesis team.” This article lays out his mechanics, gear, Eidolons, recommended teams, and gender-switch walkthrough all in one place.

1. Character Basics

Item	Details
Chinese name	零 (primary) / some early translations used “朔”
English name	Esper Zero (full name) / Zero (nickname) / The Appraiser (title)
Rarity	S-Tier (some JP-server discussions call him SS / S+ Tier)
Element	Cosmos — also translated “星脈 / Starveins”
Weapon (Arc)	Solid
Role	Sub-DPS / universal protagonist / Esper-Cycle trigger (quick-swap sub-DPS); can run Main DPS but with a lower ceiling, A-Tier
Faction	Anomaly hunter under the Yiboen Antique Shop
How to obtain	Gifted free at 1.0 launch, cannot be obtained from the gacha
JP VA	Yuma Uchida (male version) + Maaya Uchida (female version) — real-life siblings cast together
CN VA	Ma Yang (male) / Cao Tong (female)
Base stats	ATK 85 / DEF 75 / HP 1,250 / Crit 5% / Crit DMG 50%

Lore Background

• The sole survivor of the seventh-tier Hypervortex disaster, found lying at the center of the New Helios disaster site, completely amnesiac
• Has abnormal sensitivity to “Anomalies” and can quickly sense and pinpoint the Anomaly core / Nexus, earning him the title “The Appraiser”
• After a brief detention and observation by the Anomaly Management Bureau, he was assigned to the cash-strapped Yiboen Antique Shop, working as an Anomaly hunter in his appraiser role
• Exclusive gender-switch feature: requires completing the hidden side quest “In the Reflection” to unlock

2. Skill Kit

Normal Attack 【Appraisal】

• Multi-hit combo dealing Cosmos DMG, generating Starvein particles to speed up energy buildup
• Lowest investment priority (★★☆☆☆)

Skill / Alternate-Track (E) 【Appraise and Engrave】⭐ Core

• 16-second cooldown
• Multipliers: weapon hits 20% + 20% + 125.6% + 134.4% / extra damage 200%
• ⭐ Core mechanic: Cycle Rate set to 100 — one press fully charges the elemental-reaction gauge and instantly triggers the Esper Cycle
• ⭐ The only character in the game who can instantly charge and instantly trigger an elemental reaction with a single press
• Investment priority: ⭐⭐⭐⭐⭐

Ultimate (Q) 【Divide by Zero】

• Energy cost 100 / cooldown 15 seconds
• Multipliers: 132.7% + 5.3% × 4 + 177.5% + 168.6%
• ⭐ Zero’s main damage source, where most of his output is concentrated
• Investment priority: ⭐⭐⭐⭐⭐

Support / Passive 【Appraiser / Rift Blossom】

• Swap-in trigger: when the active team member gains Ultimate energy, restore team HP = 50% of Zero’s base ATK
• This is the “swap-in instant charge + bonus healing” design

Combo Routine (standard quick-swap)

1. Jiuyuan Skill (deploy Lethal Rose Pact)
2. Swap to Sakiri → charged Skill (Devour Whole) to group enemies + Ultimate attack buff
3. Swap to Zero → Skill (instantly max elemental reaction) → Ultimate Divide by Zero
4. Swap to Nanally → trigger Blossom Esper Cycle → Skill (+30% Crit) → Ultimate + Normal Attack
5. Swap back to Jiuyuan → Ultimate to settle Rose Pact

Key point: all of Zero’s rotations are “enter → Skill to instant-cycle → Ultimate → exit,” completed in 3–5 seconds.

3. Eidolons / Awakening (Cosmic Insights)

#	Name	Effect Summary	Recommendation
A1	Blooming Gaze	Skill adds a 200% ATK hit; ignores 75% DEF against enemies below Zero’s level	⭐⭐ niche at endgame
A2	Finding the Calling	Grants 8 Ultimate energy after using the Skill	⭐⭐⭐⭐⭐ most crucial
A3	Anomalies Record	Ultimate Crit Rate +50% + the “Discern” resonance grants Normal Attack / Skill / Ultimate level +1	⭐⭐⭐⭐⭐
A4	Undecided Factors	Each point of base ATK increases Ultimate damage by 0.1% (cap 25%)	⭐⭐⭐
A5	Theopneustos	After triggering the support skill, ATK +10% for 20 seconds	⭐⭐⭐⭐
A6	Deceptive Liberation	Skill extra damage multiplier 200% → 300% ATK + the “Zero Display” resonance grants the whole team ATK +12% / 20s when a Cosmos character triggers an elemental reaction	⭐⭐⭐⭐

Recommended Eidolon Order

A2 > A3 > A6 > A5 > A4 > A1

• E0 playability: extremely high — Zero’s core value is the “instant cycle charging” mechanic, which is 100% unlocked at E0
• Most crucial A2 (Ultimate energy +8) makes Zero’s Q loop seamless
• Next-most-crucial A3 (Ultimate Crit +50%) keeps the Ultimate critting reliably

4. Best Gear

Two Arc (Weapon) Choices

Arc	Source	Effect	Verdict
Doomrain	Limited Press bundle (US$2.99) including 180 Crystals + the Arc / not in the gacha pool	Alternate-Track and Ultimate Cosmos DMG +30%; Cycle Intensity +36 for 15 seconds after the Skill	Theoretical best, but just grab the cheap bundle if you want it
⭐ Day Off	Free (Eclipse hidden side quest)	The only Energy Recharge sub-stat in the game, 33%; ATK +30%; within the 40-second Eclipse domain, restore 6 Ultimate energy per enemy killed (up to 5 times, 300s CD)	Top free weapon, strongly recommended
The Forgotten	Standard pool	ATK +20% above 50% HP; DEF +20% below 50% HP	A passable alternative

Strong Recommendation

• ❌ Do not pay to pull Doomrain (although the US$2.99 bundle price is acceptable — that’s your own call)
• ✅ The free Day Off is already excellent — the 33% Energy Recharge is the key stat that gets Zero to a “seamless Ultimate loop”
• ✅ Save your resources for the limited characters that actually need them

For the detailed Eclipse side-quest walkthrough, see the Eclipse side quest.

Gear: Lost Radiance 4-Piece

Pieces	Effect
2-piece	Cosmos DMG +10%
4-piece	Ignore 25% DEF for 20 seconds after the Ultimate (cannot stack)

Alternative: Shadow Creed (2-piece ATK +10% / 4-piece ATK +25% for 20 seconds after the Skill)

Main Stat + Sub-Stat Priority

Slot	Priority
Main stat	Crit Rate (mainstream) or Cycle Intensity (quick-swap teams) > Crit DMG > ATK%
Sub-stat	Crit DMG > Crit Rate > Cycle Intensity > generic DMG bonus > ATK%

Module Layout: II × 2 + III × 4 + IV × 1 (total +40% ATK)

5. Recommended Teams

Wave Team (mob clearing / elemental-reaction loop)

Zero + Nanally + Jiuyuan + Sakiri

• Main DPS: Nanally (Anima, triggers Blossom)
• Sub-DPS: Zero (instant cycle charging)
• Sub-DPS: Jiuyuan (Anima, Rose Pact chain damage + secondary healing)
• Support: Sakiri (Lakshana, grouping + ATK buff)
• ⭐ Core: pairing Anima + Lakshana unlocks the Charge reaction, with Zero handling instant triggering

Boss Team (high-HP single target)

Zero + Nanally + Hathor + Sakiri / Fadia

• Hathor (Lakshana shield type) buffs Remora and provides survivability
• Fadia provides damage sharing and break resistance

Time-Stop Team (ultimate endgame lineup) ⭐

Zero + Hotori + Nanally + Sakiri / Jiuyuan

• Hotori’s “Skill Replay” memory + time-stop mechanic = the strongest team in the game
• Zero instant-charges the reaction → Hotori memorizes → Ultimate replay = double Blossom-trigger burst damage

F2P Lineup

Zero + Mint + Skia + Haniel

• Mint (Anima Main DPS), Skia (Lakshana, buffs Remora), Haniel (buffer)
• A low-investment team of pure A-tiers + the protagonist

6. Investment Priority

1. Level breakthrough to 80 (the current 1.0 cap)
2. Skill leveling order: Skill → Ultimate → support skill → Normal Attack
3. Max out the Day Off Arc (free, prioritize the breakthrough)
4. Lost Radiance 4-piece (main/sub-stats per the priority above)
5. Awakening / Esper upgrades: A2 → A3 → A6 → A5 → A4 → A1
6. Unlock Resonances: A3 Discern (skill level +1), A6 Zero Display (whole-team ATK +12%)

7. Gender Switch (In the Reflection) Walkthrough

Unlock Conditions

1. Complete the main-story Prologue Chapter 2 “Good Business, Better Treasure”
2. Unlock the scooter vehicle
3. Head to Hankaku Street in Bridge Crossings
4. Overhear two girls discussing a “mysterious mirror Anomaly” to start the side quest

Quest Steps

1. Enter the shop and talk to the NPC Kookie
2. Walk to the washbasin in the corner of the shop
3. Perform Add Water at the washbasin
4. The water’s surface reflects the opposite-gender version of Zero
5. Quest complete

Rewards and Switch Rules

• Unlocks the Switch Appraiser feature (Settings → Other tab)
• Bridge Crossings footprint points +50
• Switchable once every 24 hours
• ⭐ All CGs, voice, and story portraits switch along with it (the Japanese dub auto-swaps between the Uchida siblings)
• The male / female versions have identical combat stats, skills, and Eidolons — purely an appearance + voice difference

For the detailed side-quest breakdown, see Story & Hidden Side Quests Deep Dive.

8. Community Memes / Reception

• The “gender-switch system” is exclusive — the only protagonist who can freely swap gender since launch
• “Real-life siblings cast together” — Yuma Uchida (male version) + Maaya Uchida (female version), a rare gem in the Japanese voice-acting world
• “Universal / multi-purpose protagonist” — fits into any team, because “instant reaction triggering” is a universal mechanic
• “Instant-cycle-charging machine” — Skill Cycle Rate = 100, a mechanic exclusive to the whole game, making Zero essential for quick-swap playstyles
• “The indispensable loop-trigger of the Synthesis team” — together with Nanally (Anima) + Jiuyuan (Anima / Lakshana dual-fit), he forms the core of the Charge-reaction Synthesis team
• “Free T0 Sub-DPS” — multiple guide sites (GameWith / Game8 / Kaiden) unanimously rate him as “one of the most worthwhile free launch protagonists ever”
• Weakness discussion: he is a burst-type Main DPS, his sustained damage over time is insufficient, and his endgame Main DPS ceiling is limited (A-Tier, not SS)

9. Zero vs Other Free Launch S-Tier Characters

Comparison	Zero (protagonist)	Sakiri	Chiz (Urban Tycoon gift)
Source	Launch gift	Launch gift	Tycoon Lv 18 gift
Element	Cosmos	Incantation	Cosmos
Role	Sub-DPS / reaction trigger	Support / Buffer	Main DPS
Eidolon / signature Arc	Eidolons need pulling / Doomrain available cheaply	Basic version included at launch	Tycoon gifts 6 Eidolons + 5 signature Arcs
Gender switch	✅ Unique	❌	❌
Team importance	⭐⭐⭐⭐⭐ Must-field	⭐⭐⭐⭐⭐ On every team	⭐⭐⭐⭐ Budget Main DPS

Related Guides

• Signature Arc Complete Guide — full Doomrain vs Day Off comparison
• Gear (Cassette) System Complete Guide — Lost Radiance set
• Story & Hidden Side Quests Deep Dive — Eclipse side quest + In the Reflection
• Nanally Complete Build Guide — main Synthesis-team partner
• Jiuyuan Complete Build Guide — Wave-team core
• Hotori / Firebird Complete Build Guide — Time-Stop-team core
• NTE Voice Cast Deep Dive — the Uchida siblings in depth

FAQ

Esper Zero data compiled from public sources including Game8, GameWith, Kaiden.gg, Mobalytics, Prydwen, Icy Veins, TheGamer, GameRant, Dot Esports, Fandom Wiki, HN PlayNews, LDPlayer, enjoyGM, Bahamut, Moegirlpedia, and others. Some skill multipliers may be tuned across versions — the in-game values are authoritative.