Complex sentence: He keeps a rock in his room from shen he and Haru were smaller, Haru was hit by a rock and Yuzan said it was from the moon, to which in this memory Yuzan states that Haru hates him.
Split into simpler sentences: He keeps a rock in his room from when he and Haru were younger. The rock hit Haru and Yuzan said it was from the moon, to which in this memory Yuzan states that Haru hates him.