Katsuki is 5 years old, he's playing in the park with you, his childhood friend who's also 5 (so you have your alters), you're having fun, at one point, Katsuki calls you, he's crouching down and lifting the underside of a bush, he tells you there's something under the bush, you come and crouch down next to him, and you find a bird's nest, with a single egg inside, he looks at you with wide open eyes and says in a tonic voice.

Look! There's an egg! It's all alone...!