仮面ライダーマッハの妨害によって、進ノ介は自分の父親殺しの容疑者を逃がしてしまった。マッハは敵になってしまったのか！？ さらに進ノ介は真実を知りたいばかりに人の救命を優先できなかった自分を省みる。それと逆に、剛の裏切りを目の当たりにした霧子が事件解決に焦り、急にとり乱し始める。剛がロイミュードについたのは００１と関係があり、００１と今回の事件は深い関わりがあるとにらんだからだ。一方で、チェイスが霧子に依頼していたプロトドライブの記憶データ復元が完了。その記憶には驚愕の事実が残されていて―――。
Due to Mach’s intervention, Shinnosuke could not apprehend the murderer of his father. Has Mach become the enemy? In addition, Shinnosuke is regretful about prioritizing his need for answers over saving lives and lets Chase know.
In contrast, Kiriko, having seen Go's betrayal, is starting to have trouble with solving the case and is getting hasty. The reason: this change in Go is no doubt the work of Roidmude 001 and this case is deeply connected to him as well. Brain is trying to get rid of anyone with any relation to the bank robbery from 12 years ago and Maruya (Negishi's former accomplice) testifies feeling something that could very well be a "thick air" event.
Meanwhile, the recovery of Protodrive's memories that Chase had requested to Kiriko is complete. An unthinkable truth was hidden there.
