Cube Entertainment revealed, "Eunkwang's fans wanted to do something nice for his birthday and started collecting donations for the Korea Diabetes Association, which BtoB works as ambassadors.

"[11] On April 9, 2019, while serving the military, Seo donated ₩20 million to help the affected areas of the Sokcho Fire through Hope Bridge National Disaster Relief Association.

[13] In April 2020, BtoB's fan club 'Melody' donated women's hygiene products to commemorate Seo's discharge.

The fan club delivered 3,201 sanitary napkins and wipes through World Human Bridge for pregnant women in vulnerable families who are suffering from COVID-19.

[15] Seo debuted as the leader and main vocalist of Cube Entertainment's boy group BtoB on March 21, 2012, with the promotional single "Insane".

A music video was uploaded to BtoB's official YouTube channel, featuring 4Minute's Nam Jihyun and singer Roh Ji-hoon.

Due to the sudden news of his enlistment, he was only able to perform 6 of the shows for Barnum: The Great Showman despite practice.

[28] On April 25, 2020, Seo broadcast a 12 hours YouTube Live, 'Silverlight Is Back' on Btob's official channel to celebrate his discharge from the military.

On August 13, 2020, Seo's appointment as a member of Cube Entertainment's board of directors was revealed through the company's 2020 half term report.

On October 27, 2020, Cube announced that they have formed a unit called BtoB 4U consisting of Eunkwang, Minhyuk, Changsub and Peniel.