Girl from Nowhere

Both are Thai horror dramas that have some supernatural elements. In Girl from Nowhere, the main character is a girl that is a supernatural entity that punishes all the wicked students. Meanwhile, in Dead Friend Forever, the main character is a boy that is missing/dead and everyone of his classmates involved in his misery/death is punished for it. DFF has some male-male relationships although horror is the main focus instead of romance unlike a traditional BL.

Both dramas are centered around a girl who is willing to do anything and everything to get her revenge. Both girls can be described as anti-social/sociopathic beings.

Both are a supernatural/fantasy thriller centered in school, and shows a lot of bad things people can do to be accepted in school and in life. In Girl From Nowhere the FL is the "ghost" and, in Detention, the FL kinda has to deel with the ghost.

A mysterious, clever girl named Nanno transfers to different schools, exposing the lies and misdeeds of the students and faculty at every turn

Similarities: a supernatural being infiltrating the school and exposing lies of cheaters and those who commit sins in a sinister cat and mice game.

The Girl From Nowhere series contains a certain feel and vibe that is present within some of the episodes of On Children. This vibe being a more dark and psychological look on society, using different elements to metaphorically display a person's hidden evil self. It is also similar as in both shows, each episode is set in a different setting.

Both have that psychological & high school elements to them. They are not the same though, Extracurricular is not an anthology. But it centers around high school kids doing illegal activities.

both tell a different story per episode
series uses supernatural recourses
both are open to show violence, blood or sexual content

In "Kesenai "Watashi": Fukushu no Rensa", Shoko carries out the revenge on the bullies who ruined her life. In "Girl From Nowhere", Nano acts as the representative for those who were wronged by dealing out karma, getting revenge and ruining the lives of perpetrators.

~ Girls coming in and getting revenge on others.
~ The thriller aspect of how those who did wrong are dealt with.
~ You slowly go through the media learning what they did wrong instead of all at once.