Complex sentence: After the tournament, Negi takes part in more activities at the festival until Chao makes her move as she reveals herself as a time-traveler who chaims she must change the present to avert a great catastrophe in the future.
Split into simpler sentences: After the tournament, Negi takes part in more activities at the festival. Until Chao makes her move as she reveals herself as a time-traveler who chaims she must change the present to avert a great catastrophe in the future.