When digivolving with this card's [When Attacking] effect, paying the digivolution cost moves the memory gauge to 1 or more on my opponent’s side. What happens to the attack?
Show ruling
The attack continues, but the turn doesn't switch over yet. If the memory gauge is still at 1 or more on your opponent’s side after the attack has ended and all effects triggered by it have been activated, only then does the turn end.
Source: EX1-040 MegaKabuterimon