How kaneki lose his memories?
Kaneki lost his memory after Kaneki lose his memories in Tokyo Ghoul fight against Arima (CCG) where he pierced both his eyes. Thanks to Kaneki’s regenerative abilities, his brain rebuilded itself to allow him to survive, however his memories couldn’t be “regenerated” and were, unfortunately, lost.
Does kaneki keep his memories?
He later regained his memories during the Tsukiyama family extermination where he fought Tsukiyama Shuu, his guard-like servant (Karren) and Eto Yoshimura (The One-Eyed Owl) alone.