Maybe because the guy had his best gear in move 4 and he is not aware of it. If the difference between his real move 4 initiative and your real move 3 is higher than 10k then he moves before. Lets say in matsuri his move 4 has the stats of his equipped move 1 and owns 18000 initiative, if your real move 3 has 6000 initiative then he is able to interrupt you.

That's what the team said to jiburiru but not what we all see that happens for real. If this was true would be close to impossible to see move 2s with inverted order in comparison with move 1s to not talk about moves 3s vs 4s and i am sure it never happened to you while facing people stronger than you by far (to me happened two times yesterday out of 6 battles and is not that my move 2 treasure tool is so op... but i went ahead the same).

What happened is that your mystery was delayed. You were not actually interrupted but, server side, your ninja died before the server received you mystery input so, even if your ui showed you the icon of your mystery in truth the mystery was not calculated in.

Can you tell us how they were placed on the field your and his ninjas? I begin to think maybe the enemy main was not in 4th prompt move (moreover because there are not many meta lineups that put mb with acupuncture seal in move 4... )

Ok, i understood what happened - i think - you just had used kushina mystery in that round, somehow you endured 6 hits with her and the cd got reset so you clicked or the auto did it for you on her mystery again, but since the mystery couldn't go off again in that round was delayed to the following round. In that case can be interrupted even by slower mysteries. Every dance of impetus user know about this.