Goseki Koichi

 (五関晃一) is a Japanese idol, a member of A.B.C-Z, a former member of B.B.A., a former member of Secret Agent, and a former member of B.A.D..

He joined B.B.A. in 1998 and left in 2001 where they ceased activities.

He left Secret Agent in 2000 where they ceased activities.

He joined B.A.D. in 2001 and left later the same year.

He joined A.B.C-Z in 2002.

Discography Featured In
A.B.C-Z=
 * Albums
 * from ABC to Z
 * A.B.Sea Market
 * ABC START LINE
 * 5 Performer-Z
 * VS 5
 * Going with Zephyr


 * Single
 * Moonlight walker
 * Take a "5" Train
 * Reboot!!!
 * Shuuden wo Koete ~ Christmas Night / Bounenkai! BOU! NEN! KAI!
 * JOY Shitai Kimochi
 * Black Sugar
 * DAN DAN Dance!!
 * Cheat Time


 * DVD Singles
 * Za ABC ~5 Stars~
 * Zutto LOVE
 * Twinkle Twinkle A.B.C-Z
 * Walking on Clouds
 * Never My Love
 * Legend Story
 * SPACE TRAVELERS
 * Hana Kotoba


 * Video Releases
 * ABC Za Hoshi (Star) Gekijou
 * Johnny's Dome Theater ~SUMMARY2012~ A.B.C-Z
 * Shounen Tachi Jail in the Sky
 * A.B.C-Z 2013 Twinkle×2 Star Tour
 * ABC Za 2013 Johnny's Densetsu (The Digest)
 * Summer Concert 2014 A.B.C-Z★"Legend"
 * A.B.C-Z Early summer concert
 * A.B.C-Z Star Line Travel Concert
 * ABS Za 2016 Kabushikigaisha Ouenya!! ~OH&YEAH!!~
 * A.B.C-Z 5Stars 5Years Tour
 * ABC Za Johnny's Densetsu 2017
 * A.B.C-Z 2018 Love Battle Tour
 * A.B.C-Z Concert Tour 2019 Going with Zephyr


 * Collaboration Video Releases
 * JOHNNYS' World no Kanshasai in TOKYO DOME


 * -|Secret Agent=
 * Singles
 * Secret Agent Man