21st Century Boys Vol 2

From the VIZ Media edition

The climax of our story is finally at hand! Mankind faces a crisis, and Kenji is hustling to save the world and the people he loves. But he also must solve the mystery of the Friend. Who is he and why did he become evil? The answer is tied to a memory Kenji has from when he was a twentieth century boy.

Source: Anime News Network Encyclopedia