And it's not just levels for the users -- each one has their own play style in how much or how often they play. So catering to a wide audience must be a challenge.

KK: It definitely is. I don't want to portray the social game audience in terms of those who engage in monetary transactions and those who don't, but for example, if you tune a game's balance for the paying the users, the non-paying ones will never stand a chance. I think we have the expertise you need to make a game that appeals to both paid and non-paid users, but if you don't have any experience with that, I don't think you could do it.

For example, with PVP games like Ninja Royale, a paying user will have an advantage over a non-paying user. How do you make it fair?

KK: That lies at the root of the whole game. Which random users which carry treasure show up on the listing that you receive really does lie at the core of it, so I can't give you real details about it.

It's a matchmaking problem.

KK: It is, and it's one we have to treat very carefully.

In free-to-play games, there are a lot of different philosophies about whether items should give direct advantages or indirect advantages, from developers in the West.

KK: We're certainly different from Zynga in that respect. Both Kaito and Ninja Royale are games where you're gathering treasure, but if users could get this treasure via paid items, then the game balance would fall apart. There wouldn't be any meaning to it; you'd be ruining the core of the game.

What we sell instead is the opportunity to make treasure gathering easier. For example, have you played mahjong? This may work with poker, too. If you're one card away from a royal flush, you only get one chance to draw that card. Well, what if you paid 100 yen [$1.31] and get three chances instead? (laughs) Which do you think is more interesting to the user: very difficult odds, or a chance at easier odds?

Ninja Royale

The chance is what makes it interesting.

KK: It is. That in itself is interesting. Paying out has to be interesting in itself, I think. We're selling chances, and it results in some interesting reactions from the users. For example, if you go out to buy toilet paper, there's nothing really fun about that. You pay money, and you get toilet paper. There's no volatility, so there's no feeling of excitement.

But let's say -- this isn't quite volatility -- when you go to the Apple Store and buy a MacBook, that's more exciting. Giving users the opportunity to spend money and get something really exciting as a result is really neat, I think. The act of spending money, in itself, becomes appealing and fun -- like "Okay, here goes!" So it's a similar sentiment when you're near that royal flush; you're excited. That's the important thing.

It's fun deciding what kind of MacBook you want.

KK: There is that, yes. There are several ways for it to be fun for people to spend money. There's volatility; the chance of something really fun or something not so fun, as well as that "Here goes!" feeling we talked about earlier. There's also the fun of buying a present for someone and imagining how he'll respond, if he'll wonder who it's from. You have to include those sorts of features.

Some of the examples are a bit close to gambling, though.

KK: Well, I don't think gambling is a bad thing, but the difference from gambling is that with gambling, you potentially have money coming back at you. Pachinko wouldn't be such a huge thing if money wasn't coming back to players.

It's not a bad thing, but don't you think it's a little dangerous?

KK: What do you mean?

You could lose a lot of money, or get too involved in it.

KK: The thing that I worry about the most is whether or not the user is getting excitement, or entertainment, that's commensurate with the money he's using. For example, having three chances at a royal flush for 100 yen; that's not a terrible way of balancing it. You approach it from the same philosophy as if you're buying a can of juice, except it has the potential to bring even more excitement.

If you tried to find a way to get a similar feeling of excitement for 100 yen with some other form of entertainment, that's going to be tough. Social games offer just a certain amount of stress and release to users.

Beating the final boss of Final Fantasy XIII would certainly produce a lot more excitement, but you have 60 hours of gameplay to get through for that, which also contributes to that big release. I think that users were looking for a lighter, more accessible form of entertainment, and providing that sort of entertainment, or sense of achievement, for the price of a can of juice is something I think is very neat.