what is the korean movie or drama series where a mother feed human to her monster son?

The Korean drama you’re describing is almost certainly Gyeongseong Creature (경성크리처) on Netflix.

What matches your description

In Season 1 , the main monster is revealed to be Chae-ok’s mother , who was turned into a creature through horrific experiments at Ongseong Hospital. The key scenes that match “mother feeds human to her monster son” are:

• A Japanese official orders the creature (her transformed child/son figure) to devour Chae-ok (his daughter-figure).

• Instead, the creature refuses the order , protects Chae-ok, and in some interpretations appears to be fed / offered humans by the soldiers, while the mother-creature tries to shield her child.

Some viewers summarize this as “a mother (now a monster) being used to feed humans to her monster son,” though technically the creature in those scenes is more of a son-like figure created from experiments, and the mother is the monster protecting rather than feeding him. The emotional core is: mother turned into monster still recognizes and protects her child.

About the series

Title: Gyeongseong Creature (경성크리처)
Platform: Netflix
Starring: Park Seo-joon, Han So-hee, Claudia Kim
Setting: 1945 Gyeongseong (now Seoul) under Japanese occupation, with a second season jumping to 2024 Seoul.

Genre: Historical horror, mystery, creature thriller.

The story is inspired by the real-life atrocities of Unit 731 , with Korean civilians subjected to secret biological experiments that create the creature(s).

Not the only possibility, but the closest

There is another Korean series with a monster child and dark family themes: “It’s Okay to Not Be Okay” , which has a fairy-tale segment about a “zombie child” and a mother, but it does not involve a mother feeding humans to a monster son in the way you described.

So the show you’re remembering is almost certainly Gyeongseong Creature , especially the first season’s revelation that the monster is Chae-ok’s mother and the scenes where she is forced to confront orders to eat her daughter while trying to protect her child.

Information gathered from public forums or data available on the internet and portrayed here.