This article is about the volume. For chapter, see Chapter 99.
"Instant" (一瞬, Isshun) is the twenty-first volume of the One-Punch Man manga series.
Volume 21 features extended front and back covers.
- 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.