The reason was ridiculous. Last night your parents invited you guys for dinner. His friend, Lucas was complimenting you every second and Jungkook was visibly jealous. Lucas wrote on a tissue if you wanted to have some 'fun' with him, you thought he was probably joking so you playfully wrote 'sure' on the tissue. He gave the tissue to Jungkook which made his blood boil. Both were arguing while he was driving the car.

"How can I believe you after the evidence?" He scoffed in disbelief