I was never much into k-pop, never "worshiped" the artists, so from spiritual point of view I probably wasn't very deep in it. Leaving it all behind didn't trigger anything bad. And by leaving it behind I mean everything, even dropping the "digging into k-pop and occult dirt that's behind it" on this forum.
On the other hand, when I got here and started to read this and BTS thread, that's when I was spiritually attacked. I went through it in the past so I knew what I was dealing with. Very distinct, life and happiness sucking, fear and depression boosting feeling that came in a matter of seconds, it felt like a heavy coat. Also had one weird dream with RM. I prayed over it, rebuked every evil spirit behind it in the name of Jesus, asked Him to wash me with his blood, just asked for His help and protection during sleep. Thank God, I never had any other k-pop related dreams, the "heavy coat" was lifted after few minutes of prayer, and I felt it literary lift off of my shoulders in a matter of a second, and leave.
Peaceful mind is a treasure one has to take care of. A lot depends on what kind of info and stimuli you feed your mind with. If you keep digging in the dirt, even if it's only for research, don't be surprised when you dream about it or end up depressed. If it's spiritual oppression, it will most likely not go away by itself, one has to know how to pray to be delivered. Or you'll get used to it after some time, but that's not good. You can always ask Jesus for help, feel free to use your own words
“The Lord is Near! Do not be anxious about anything. Instead, in every situation with prayer and petition with thanksgiving, tell your requests to God. And the peace that surpasses all understanding will guard your hearts and minds in Christ Jesus.” Philippians 4:6
"I will lie down and sleep in peace, for You alone, O LORD, make me dwell in safety." Psalm 4:8