![ONF 2021 LIVE CONTACT :: CODE #1. [REVERSE]](https://image.tmdb.org/t/p/original/4wjPi5x2igYJI9jrbE5QcJhSW8X.jpg)
[Reverse] is the first concert held by ONF. It was held across four days from December 9-12, 2021, at Yes24 Live Hall in Seoul, South Korea.
Mizuguchi Yuto, better known by his stage name U, is the vocalist and dancer of the boy group ONF. He was a JYP Entertainment trainee. He participated in MIXNINE and came in 23rd place, hence eliminated.