Fusion is an ability that Neku and his partner can perform to deal varying amounts of damage to all Noise in the area, and to heal a varying amount of damage. These Fusions are activated by tapping a Harmonizer Pin, given to Neku and Shiki at the end of the second day. Each partner has 3 Fusion levels; each successive level does more damage and heals more HP.
Fusion is gained by obtaining Fusion Stars in a partner's card minigame; Shiki's ESP Cards, Joshua's High and Low Cards and Beat's four suits in a deck of playing cards. Any unused fusion stars are carried over to the next reduction in a chain battle, but are lost at the end of the chain. Excess stars are also lost if a Fusion is performed with more than the required number.
To perform higher level attacks, Neku's partner must collect more Fusion stars. For them to use level 2 on their first Fusion attempt, for example, they need to collect 8 stars instead of 4 by ignoring the Fusion pin when it appears, and continue to collect stars. A level 3 fusion attack requires 16 stars. Neku and his partner can only use level 2 or 3 fusions if he obtains its respective sticker through a shop quest.
Every time Neku and his partner use a fusion in a chain battle, the star cost for all fusions goes up by one, to a maximum of four additional stars required. The cost is reset when the chain ends.
The damage dealt by a fusion is as follows:
- DAMAGE = EFF x ATK x DIFF
- EFF: The efficiency factor of the Fusion, depending on its level and who Neku's partner is:
- Shiki: 5 (lvl 1), 10 (lvl 2), 20 (lvl 3)
- Joshua: 5 (lvl 1), 15 (lvl 2), 99.99 (lvl 3)
- Beat: 10 (lvl 1), 20 (lvl 2), 30 (lvl 3)
- ATK: Neku or his partner's Attack, modified by threads.
- DIFF: The Difficulty multiplier, as follows:
- Easy: 2.00
- Normal: 1.00
- Hard: 0.61
- Ultimate: 0.40
The damage is dealt separately on each screen, using the appropriate character's Attack. Enemies that have temporarily left the battle area, such as shrews or dived sharks, are not harmed by the Fusion on the screen where they are not visible. Enemies that are simply outside Neku's current field of view, but still in his battle area, are harmed.
In The World Ends with You -Solo Remix- and The World Ends With You Final Remix, the Stride Battle Cross System has been removed to better support the new platforms. ESP'er Cards are no longer in play, and Fusions are gained from Sync Rate. Every 100% Sync Rate you and your partner get, you may use a Fusion. Cross Combos have also been added to increase Sync Rate significantly.
During fusions, you may play mini-games to increase the Fusion's Attack Power, and Drop Rate. The attack multiplier starts at 1.0 and rises by either 0.1 or 0.2 with each iteration (there appears to be a preset pattern for whether a specific ordinal boost will yield a 0.1 or 0.2 increase). Each partner's Mini-Game is different. After the mini-game's time runs out, the Fusion will commence at the specified power. Due to the lack of dual screens, some Fusion animations have been changed.
In Shiki's Mini-Game, you must tap the two matching cards with the same symbol as the Card you see on the top of your screen. With the exception of the top card, the cards will only be revealed for a brief moment when you must memorize them (the top card is visible before the others flip). The number of cards will increase each round, maxing out at 6. Each successful match adds to the multiplier. Finding both matches without mistakes adds an additional per round. A mistake reduces the remaining time for the mini-game
In Joshua's Mini-Game, you must tap the numbers in 1, 2, 3 order. At first there will only be 3 cards, but up to 5 cards will appear in subsequent rounds. The extra cards will carry a number of 2 or 3, but displayed backwards. Each correct card tapped adds to the multiplier. Each round cleared without mistakes adds an additional Every mistake reduces the remaining time.
In Beat's Mini-Game, you must make two cards in a line match. Tap the card(s) that don't belong to create a pair. You can also make combos when you make a pair, and the two cards behind the pair match each other.
Each partner is limited to level one fusion at the beginning. Completing shop quests for Fusion Stickers can increase this limit. Locations are as follows:
- Shiki: "Ready to die?"
- Neku: "Then die!"
Level 1: Neku, Shiki, and Mr. Mew attack each enemy.
- Shiki: "Neku! Come on!"
- Neku: "Right behind you!"
Level 2: Shiki and Neku ride large versions of Mr. Mew while he attacks with multiple normal size copies.
- Shiki: "Go Mr. Mew!"
- Neku: "Get 'em, Piggy!"
Level 3: Mr. Mew grows to an enormous size and fires energy beams from his eyes while Shiki and Neku stand on his shoulders.
- Joshua: "Follow my lead!"
- Neku: "Screw that!"
Level 1: Neku and Joshua drop various street objects on enemies.
- Joshua: "Works for you?"
- Neku: "What do you think?"
Level 2: Joshua attacks enemies with ice and Neku attacks enemies with fire.
- Neku: "Another world awaits..."
- Joshua: "And you're going."
Level 3: All enemies on the battlefield are hit with the moon.
- Beat: "Pick it up, Phones!"
- Neku: "I'm there!"
Level 1: Beat and Neku repeatedly slide across the screens before teleporting away.
- Beat: "The beat is on!"
- Neku: "Bring it!"
Level 2: Chains form across the screen, Beat and Neku ride along the chains.
- Beat: "Let's start it up!"
- Neku: "No, let's end it!"
Level 3: Beat and Neku surf a wave that consumes enemies.
Uzuki Yashiro's and Koki Kariya's fusionEdit
Like Neku and his partners, Uzuki and Kariya also have a Fusion. They each get on one side of Neku and begin simultaniously blasting him with puple lightning. They only demonstrated this while under the effects of the O-pins so it's unclear if they can do this naturally.
Final Stars FinishEdit
This Fusion appears in order to defeat the final boss of the main story. It appears to use all 4 protagonists energy to mark a foe with a white X, which proceeds to annihilate the foe with white bolts of energy.
- Uzuki Yashiro and Koki Kariya are the only other characters shown to use a Fusion attack. Unlike Neku and his partner's Fusion attacks, they do not seem to be obtained with fusion stars, as Uzuki has no combo map. Instead, they will automatically execute the Fusion attack (which does not heal and only affects one screen, unlike Neku's) after five passes of the Light Puck. They are also the only other characters to use a light puck.
- Noise 44, Progfox, is the only Noise to have a Fusion-like attack.
- Joshua's Level 3 fusion is the only fusion to have a polarity; negative. It is also the only fusion where Neku speaks first.