My eyes were full of tears when the episode revealed why Eren's belt was broken. In my opinion, Keith was surely in love with Carla and he simply wanted to shield Eren from the harm. But when he saw Eren struggling and prevailing, he must be reminded of the words Carla said, 'he's perfect and special by himself'. That's why he changed his mind and said to himself silently 'Grisha, your son became a military man today.'
