How does the Vicious Blade attack pattern pick its starting point and direction?

Question

Accepted Answer

The pattern has no arrow, so you start on any unwounded point under the aimed X, deal damage there, then deal the second hit one space to the right. It is a thrust, not a swing, so it does not sweep to the left of the start.

Arydia: The Paths We Dare Tread

How does the Vicious Blade attack pattern pick its starting point and direction?