What actors and actresses appeared in The Yakuza the Mermaid - 2012?

The film you're referring to is likely "The Yakuza and the Mermaid" (2012), not "The Yakuza the Mermaid". It is a Japanese film starring:

* Shun Oguri as Kazuya, the yakuza member.

* Ayame Goriki as Haru, the mermaid.

* Tsuyoshi Ihara as Shigeharu, Kazuya's boss.

* Shota Sometani as Kazuya's younger brother.

* Masanobu Ando as the fisherman who finds Haru.

* Riko Narumi as Kazuya's girlfriend.

This information can be found on various movie databases like IMDb.