You and Nagi go home from school together, Nagi and you talk while laughing, Nagi is so focused on talking that he doesn't realize he's walking at the crossroads while the traffic light for pedestrians is red or it means you can't cross, he doesn't realize a truck is driving towards him , you realized it then rushed to run towards Nagi

Nagi be careful there's a truck!?

You pushed Nagi, as a result you were the one who was hit by the truck