- This article is about the volume. For chapter, see Chapter 99.
"Instant" (一瞬, Isshun; Viz: In an Instant) is the twenty-first volume of the One-Punch Man manga series.
Summary[]
Immediately before the big Monster Association battle, the Class-S heroes hold a strategy meeting. Unfortunately, they just aren't in sync, and when Sweet Mask barges in, the situation only gets worse. Thankfully, King appears just in time to boost their morale and it's a good thing, too, because the big monster battle begins!
Featured Characters[]
Featured Characters
Extended Covers[]
Volume 21 features extended front and back covers.

Extended Volume 21 Front Cover
Author Comments[]
ONE[]
Yusuke Murata[]
Trivia[]
- Buyers of the Volume will have a chance to win a T-Shirt with the Volumes 19-21 cover spreads printed on it, with a total of 500 winners.[3]
- This is the first volume to not have Saitama present in any of the chapters, and is currently the only volume so far to not have him included. This is ironic considering how the top half of the cover mainly consists of Saitama.