As preparations for his battle with Minuha, one of Seth's problems that he had looked to solve was the problem of the woman's ability to split herself into multiple shadows.
This ability made the woman difficult to fight, and almost near impossible to completely kill, and killing her was Seth's objective for battling her.
After mulling over the issue for a while, Seth had made two conjectures which had helped him arrive at a solution for his problem.
Firstly there was the fact that while he was seeking to kill the woman, the woman was also actively looking to keep him captive.
This fact meant that rather that Seth wouldn't have to worry about Minuha running away.
It meant that rather than Minuha just splitting her body into several shadows and making life difficult for him, the woman would have to actively engage in battle if she wanted to accomplish her goals.