Kick the Bucket

Jin-Seop, a gloomy guy working as an intern at a large corporation. His only hobby is stalking his team's assistant manager, Tae-Young, who seems perfect in every way. One day, while collecting Tae-Young's traces and feeding his delusions, Jin-Seop witnesses Tae-Young engaging in physical lobbying with higher-ups for a promotion. Feeling betrayed by the hidden side of Tae-Young, whom he thought was his own angel, Jin-Seop devises a plan to blackmail Tae-Young and turn him into his dog...

(Source: Lezhin, translated)