Seal Cycle is a sequence trick that Lucia performs to deflect the fire ball tower 3 times without having to time after the first hit.
There are many ways of doing it. The best way to do the same way as the video demonstration that is shown below Refer to Lucia Move List for the names:
Dragon Tail combo cancel into Wheel Kick → Rodeo Drive → Sky High → Spinner Top → Lock on + Jump backward → Daggers → Axe Kick
Common Seal Cycle performed in the run
