The apartment flat where the veteran with amputated legs lives is number 1408. This number is in reference to Stephen King's 1999 short fiction and 2007 film adaption of same name/number.
Based on webtoon "Sweet Home" by Kim Kan-bi & Hwang Young-chan.
The building (interior) used in this movie is the same as in zombie movie Saraitda (Alive) 2020.
Character Seo Yi-kyung is not in the original webtoon where the story is based on.
RM of BTS recently recommended this drama in a vlog. (2021)