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Ding!
<You have learned the movement-type martial art, Tiger Flash Steps>
<You have gained proficiency in using the Tiger Flash Step>
<Basic-level Tiger Flash Steps → Intermediate-level Tiger Flash Steps>
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Having memorized Bram Krauss's micro-movements, including his muscles, with Omni-Sense, Vaan easily mimicked his movement-type martial art.
And with a single attempt, he improved his mastery to the intermediate level.
Nevertheless, Bram Krauss's proficiency in the Tiger Flash Steps was at the expert level. As such, the person was not too shocked by Vaan's use of it.
If Bram Krauss knew Vaan had replicated his movement-type martial art after seeing it once, he would have been shocked out of his mind.
After all, it was a skill that took five years to master to the expert level.