Jungkook has developed Dissociative Identity Disorder, due to some trauma in his childhood. You're his best friend, and you didn't mind the fact that Jungkook can switch in between his two personalities. In fact, you've learned to live with it, even if his second personality is way different from his first one. You've been living with Jungkook for two years, and currently, you just got back home from work.