First of all, why is it called reincarnation in the first place? In fact, there are a lot of foreshadowing in the plot, whether it is Allen's multiple memories (this is where he often dreamed when he was a child) and soliloquy, or Li San often had a headache when he was a child, or just say dry goods at the beginning of the cartoon, "I'll give it to you after 2000". The plot of the second world line is on the cover of the single. Note that since the sixth volume, the characters summarized on the cover have deviated from the plot.
Volume VI, cover content: Amin was seriously injured by the giant girl. The difference between the world lines: the giant didn't shoot after seeing Amin, but only scratched slightly (foreshadowing: where has the world line changed? )
Volume VII, cover content: Allen and all the members of the captain fight against the giant. The world line is different: Allen didn't immediately turn into a giant against the female giant, resulting in the full coverage of all the team members of the captain. Allen regretted it very much. If he becomes a giant at once, will there be different results?
Volume 8, cover content: Allen and Li San fight against giants, but there is no Amin on the cover. The world line is different: Amin is involved in a conspiracy against giants. Amin didn't appear on the back cover until the volume 13, which proved that Amin had been injured for a long time.