I have been informed that any images which are not part of my collection, and have an orange background, are form the collection of a former Mod for the wfigs forum with the username STOMWIJF.
Pro-Kaku Heroes Mini Big Head Figures by Character Product
Volume 1
First released September 1st 2004, Volume 1 was available through Circle K Sunkus and ringside.jp. According to blackmarketdecibel.blogspot.com the release was celebrated with a special event at Shinkiba 1st RING Arena with guest appearances from Kazans Hayashi, Hayabusa, GOEMON and Riki Chosyu. 180,000 pieces were released throughout Japan.
Volume 1.5
Volume 3
Released on June 7th 2005. This was limited to 180,000 pieces. According to blackmarketdecibel.blogspot.com the release was promoted with an autograph signing with Takeshi Rikio, KENTA and Yoshinobu Kanemaru at two Circle K Sunkus stores.
Volume 4
Released August 22nd 2005.
Volume 5
Released November 15th 2005.
Volume 6
Released March 16th 2006.
Volume 7
Released August 8th 2006.