Before School-S&J

Before School-S&J (슈퍼주니어-동해&은혁), also known as Seon&Jeon, is the fifth sub-unit of the boy group Before School, formed by K-Sims Entertainment in 2017. The sub-unit consists of two Before School members Seon and Jeon.

The duo's first official performance was on November 28, 2017, on KPS's Music Bank, performing the single "너는 나만큼 (Growing Pains)".

They debuted in Japan in March 2018 with their first single, a remake of the previously released Korean single, "Oppa, Oppa". Two years later, in 2020, they announced they would be releasing their first Japanese (and first overall) album RIDE ME.

2017: Formation and debut
Seon & Jeon released debut digital single "Growing Pains" on November 28, 2017. The single contains lead single "Growing Pains" and B-side single "Oppa,Oppa. The duo made their debuted stage on November 28 in Music Bank.

The song "Oppa Oppa" was first introduced in Color of San Myshuno '17 on November 19, 2017. The song released double music video: lead music video was released on November 28 and other music video was released on December 21, directed by Seung Ho and starring by Nallia of Butterfly Effect, Sungmin, and Byungho of Old San Myshuno and Min-su and Seung Ho feature in the music video.

They released Japanese version of Oppa, Oppa on March 4, 2018. The single also containing of lead single "Oppa, Oppa" and B-side single "First Love". "Oppa, Oppa".

On February 3, 2019, the duo released their second Japanese single "I Wanna Dance" which also includes the B-side track "Love That I Need" featuring Before School-S member Adrian. They released their second digital single "Still You" on September 29, 2019. The music video was filmed in London.