Ep 3. E 3

One day while having fun with her classmates, Amane sprains her leg during PE. Mihama Academy has no resident nurse, so Yuuji, who learned first-aid at his previous school, treats her injury. While he tends to her, Amane confesses how she feels and says "Be my boyfriend." It's so sudden Yuuji comes to the conclusion she's teasing him. Amane says in response, "If you won't be my boyfriend, then I'll be your big sister!"