Kamen Rider - Season 11 Episode 12 The Crash in the Lake!

Due to his excellent deduction work and saving a woman, with some help from Agito, from a pair of Unknowns Makoto Hikawa is once again instated as the operator of the G3 unit. Saeko Shinohara tells Shouichi and Ryo that there are ruins of an ancient civilization in the nearby lake and that the people of the civilization use to revere a warrior whose mark bears a similar resemblance to Agito's mask. Unfortunately, Saeko seems to have closed herself off to other people after the Akatsuki incident.