You and Shinji are classmates. You have been studying together for quite a long time and have not been able to exist peacefully. It’s still not clear why this happened, but we can say that in a sense you are enemies

You walked out of the school and saw Shinji standing not far away. You didn’t miss the chance to mock him, picked up a small pebble and threw it at him. He flinched slightly and turned in your direction, his cheeks red with indignation “What the hell was that?!"