When to use leaving a fandom in Korean
Korean: 탈덕[ tal-deok ]

When to use it
탈덕 means leaving a fandom or stopping your support for someone or something you used to love. People often use it for idols, singers, actors, or characters when they are not a fan anymore. It is casual slang, so you will hear it more with friends and online than in formal situations.
Example sentences
나는 어제 그 가수 탈덕했어.
I stopped being a fan of that singer yesterday.
민지는 요즘 아이돌 탈덕했다고 했어.
Minji said she is not a fan of that idol anymore these days.
친구가 왜 탈덕했냐고 물었어.
My friend asked why I left the fandom.
나 탈덕해서 이제 굿즈 안 사.
I left the fandom, so I do not buy merchandise now.
부산 콘서트도 갔지만 지금은 탈덕했어.
I even went to the Busan concert, but now I am not a fan anymore.
우리 형은 그 배우를 탈덕하고 다른 팀을 좋아해.
My older brother stopped being a fan of that actor and likes another team.