According to the data of App Annie, Supercell and GungHo keep making money in iOS. Yesterday, they announced that they do tie-up in each other's games. It is "Cross-Collaboration".
By this tie-up, characters of Supercell's Clash of Clans appear in GungHo's Puzzle & Dragons, and characters of Puzzle & Dragons appear in Clash of Clans. These are characters of Clash of Clans re-designed for Puzzle & Dragons.
Such a tie-up technique is performed frequently in the Japanese game industry.
Examining A Unique Marketing Tool For Japanese Mobile Games: “Collaborations”/ Dr. Serkan Toto - Japan Mobile And Social Games Consulting
In addition, Puzzle & Dragons enforced a lot of similar tie-ups until now.
However, this is the first time that they cooperate with an overseas company. Furthermore, this is the first time that Japanese style "Cross-Collaboration" is carried out in overseas regions of Puzzle & Dragons, too.
Unfortunately, Supercell and Clash of Clans are less-known in Japan. On the other hand, GUngHo wants to gain players of the overseas region of Puzzle & Dragons more. This "Cross-Collaboration" is a good chance for each other. It is held for from June 24 to July 7.