October 08

Japanese Card Game Mechanics

Card Battle RPG’s such as Rage of Bahamut, Marvel: War of Heroes and Puzzle and Dragons are some of the best monetising games in the world of mobile. In Japan in particular, card games can have insane ARPU numbers such as $18 (!) meaning that customers are happy to spend a phenomenal amount of money playing these games.

Card Battle RPG’s usually have quite poor interfaces / visuals, but have incredibly well thought out core loops and heavy reliance on the Gacha mechanic which results in high monetisation. If you have not already seen it, I highly recommend reading Michail Katkoff’s excellent deconstruction of Rage of Bahamut which goes into great detail about why card games can be so lucrative.

In this post, I’m going to try to attempt to explain some of the mechanics used in Japanese card games, why they are fun, and why they create reasons to come back to a game (retention) and why they lead to increased monetisation (ARPDAU).




Evolution is one of the core mechanics in Rage of Bahamut and other Mobage games. In these games, when buying card packs (Gacha), the player does not know what cards they will receive. This means that they often receive duplicate cards, which would be useless. The player can opt to sell these duplicates, but this is not very fun and devalues the card and demotivates the player from wanting to purchase in the first place.

An answer to this problem is Evolution. Rage of Bahamut allows a player to use two of the same type of card and evolve them together to make a brand new card. This can usually be done 4 times, allowing the player to keep evolving until they make a brand new card which has a new rarity rating. This means that when purchasing new cards, getting a brand new card is awesome, but even getting a duplicate card has value. This means there is always a good reason to buy cards and this is why so many engaged users buy so many cards so frequently.

There are also different ways to evolve a card, meaning that a player can use 8 cards (for the best evolution), but also get the same result using just 5 cards. However, using 5 cards means that the end evolution is not as powerful or optimal as it could be.

When the final evolution is complete, the rarity of the card is increased, making the last version even more desirable. This is very appealing to collectors / perfectionists.


Recipe Evolution


A different type of evolution is known as “Recipe Fusion.” This is when a character or card is evolved by completing a specific set of cards or materials. This is the system used in the Japanese game Puzzle and Dragons and in that game is known as “Evo Fusion.” Puzzle and Dragons uses the specific set of cards needed with daily / weekly events. This means that a player has to figure out which Dungeon drops the specific part they need to complete the evolve. This is a relatively “core” mechanic but it has proved hugely popular with the games fans and has seen all manner of forums and wiki’s formed from avid fans who try to help each other.

Recipe Evolution is great for long term retention as it really gives engaged users tangible goals to work towards and a real sense of achievement when their award is collected. In PAD it’s not possible to get 6 and 7 star versions of characters without performing Evolution, making it a very aspirational goal to work towards.

Evo Material (the cards required to perform the Evolution) are available through Gacha, which makes Gacha even more valuable, and even more lucrative.

Enhance / Fusion


Fusion is a very common mechanic that is found in almost call RPG card games. In these games, players receive many cards over the course of the game as a reward for their actions. As a result, they end up with many duplicate or unwanted low level cards that quickly do not have any use to the player. This mechanic is therefore used to help the player get rid of unwanted duplicates and to give them a reward for doing so. Fusion always costs Soft Currency, which is also given as a reward of winning battles / logging into the game.

The difference between Fusion and Evolution is the Fusion is used to increase the level of the card being Fused, whereas Evolution changes the type of the card being evolved (and sometimes changes the rarity as a result). Cards in RPG battle games usually gain XP without having to Fuse, but Fusion allows the player to speed up the process.

Overall Thoughts

Evolution and Fusion are used to add more to the “meta-game” of a card battle game. Without these mechanics, games would be only about battling endlessly. These mechanics work so well with the battle system because:

– They give the player other attainable goals every session.- They give the player a reason to want to attain as many new rewards as possible.
– Every battle is worth taking on because you always gain a reward that can be used in some way, even if the reward is very small.
– Creates more reason to use the game’s Gacha mechanic as player’s realise it’s tough to get the appropriate cards / materials needed to Evolve.