Demon Co-Op

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Demon Co-Op is a battle mechanic in Shin Megami Tensei: Strange Journey and Shin Megami Tensei: Strange Journey Redux.

Profile

A Demon Co-Op will occur whenever a party member hits an enemy's weakness (or lands a critical hit in Redux only), and any ally of the same alignment as the one who initially hit the weakness will do a follow up attack, increasing the damage dealt.

Demon Co-Ops will have 3 levels depending on how many party members share an alignment: Lv. 1, Lv. 2 and Lv. 3.

In Strange Journey and Strange Journey Redux, there is a passive skill named "Preparedness," which will increase any damage dealt from Co-Op attacks by 25%.

There are Sub Apps exclusive to Strange Journey Redux that enhance the Demon Co-Op ability, such as the protagonist being able to participate in a Co-Op regardless of his alignment.

Mechanics
General
Dungeon - Treasure Chests - Combat - Turn - Action - Level - Experience - Party - Stats - Skills - Items - Equipment - Melee Attack - Ranged Attack - Damage (Fixed) - Guard - Escape - Accuracy - Critical - Multi-hit - Insta-Kill - Ailments - Drops - Random Encounters - Symbol Encounters - Ambush - Difficulty
Franchise-wide
Demon - Magic (Fusion Spell) - Affinities - Unique skills - Extra Skills - Macca - Yen - Magnetite - Incense - Alignment - Moon Phase System - Demon Summoning Program (COMP) - Cathedral of Shadows (Fusion - Skill Inheritance - Accidents / Special / Three-demon / Sacrificial / Sword) - Demonic Compendium - Evolution - Negotiation (Special conversation) - Rag's Jewelry - Code Breaker - Press Turn - New Game Plus - Ultimate boss - Streetpass - Password - Skill Mutation - Energy Drain - Party Talks
Shin Megami Tensei series
Terminal - Guardian (if...) - Tactical Battle (NINE) - Capacity (NINE) - RTS (NINE) - Reinforcements (NINE) - Race Shift (NINE) - Modules (NINE) - Magatama (3) - Reason (3) - Demon Co-Op (SJ) - EX Missions (SJ) - Challenge Quest (4) - Skill Potential (4/A-5) - Smirk (4) - Barrier (4) - Partners (4A) - Jade Dagger (4A) - Magatsuhi Skills (5) - Essence (5) - Glory (5) - Miracles (5) - Demon Statues (5) - Abscess (5)
Devil Summoner series
Loyalty - Personality - Mystic Change - Nemechi (SH) - Case Files (RKKA)
Majin Tensei series
Rank - Affinity (2) - Arcana (Ronde)
Persona series
Shadows / Personas (Initial / Prime / Ultimate / Ancestor / Reverse / Sub) - Skill Card - Totem (1) - Type/Subtype (1+2) - Affinity (1+2) - Rank (1+2) - Mystic Change (1+2+5) - One More (3-5+5X) - Growth Rate (1+2) - Unknown Power (1+EP) - Personality (1+2, 5+5X) - Material Card (2) - Mutation (2) - Follow Up - All-out Attack (Cut-in) - Heart Item (3) - Shuffle Time (3+4+5X) - Daily Life (3-5+5X) - Activities (3-5+5X) - Calendar (3-5) - Social Stats (3-5+5X) - Social Link (3+4) - Tactics (3-5) - Requests (3-5+5S+5X; Q+Q2) - Clock (3P+3RE+5X) - Linked Episode (3RE) - Great Clock (3RE+5X) - Theurgy (3RE+5X) - Arcana Chance (4) - Forecasts (Fusion / Weather) (4+5) - Boost (Q+Q2) - Power Spot (Q+Q2) - F.O.E (Q+Q2) - Confidant (5) - Technical (5+5S+5X) - Treasure Demon (5+5S+5X) - Party Switch (5+5S) - Baton Pass (5+5S+5X; Q2) - Disaster Shadow (5R) - Fusion alarm (5R) - Persona Traits (5R+5X) - Third Eye (5+5S+5X) - Master Arts (5S) - BOND (5S) - Persona Points (5S) - Highlight (5X) - Synergy (5X)
Devil Children series
Trainer - Bank - BattleNet - Relic Fusion - Power Fusion - Powers
Digital Devil Saga series
Berserk Mode (2)
Devil Survivor series
Devil Auction - Extra Turn Battle - Skill Crack - Titles (DSO / DS2 / RB) - Fate System (2) - Add-On (2)
Other
Equip Type (GMT:TM) - Skill Systems (GMT:TM) - Sword Exchange (GMT:TM) - Class (TMS♯FE) - Class Change (TMS♯FE) - Topic System (TMS♯FE) - Side Quests (TMS♯FE) - Ad-lib Performance (TMS♯FE) - Session (TMS♯FE) - Dual Arts (TMS♯FE)