leaving a fandom vs becoming a new fan in Korean
탈덕vs입덕

탈덕leaving a fandom
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.
When to use leaving a fandom
입덕becoming a new fan
입덕 means becoming a new fan of someone or something, like a singer, actor, drama, or game. People use it when they start to like it a lot for the first time. It is casual slang, so you will hear it in friendly conversations and online.
When to use becoming a new fanHow they differ
입덕 is the opposite direction. It means you start liking an idol, actor, or character, not stop being a fan.