Thread:Gokyr586/@comment-24440576-20150610103017

Tomari's son IS Dark Drive.

http://www.cinematoday.jp/page/N0073932

Dark Drive's identity is Tomari Eiji, Shinnosuke's son from the future. His partner is Miku and he is assigned to go back in time to kill his father by a man named Shinji

http://forums.henshinjustice.com/showthread.php?92976-Kamen-Rider-Drive-News-Rumours-Thread-1/page340  