Basically for attack you need stamina : you need a 3 battle slot from the event exploration, whereas in defence it doesn't use stamina.
Attack give 1 to 5 Perot roller ticket depending on the adversary total SED and defence always gives 3.
Perot roller ticket is similar to a gacha, but for the event.

This event is considered in Japan as the friendliest one for beginner players. Cause you don't need to have high total SED but 5 card with 4000-6000 SED to have a pretty high win rate.

We don't understand everything especially because the event have change quite a few times and the JP wiki have still some data from theses past versions.
Like Kotono I think there will also be a ranking with for sure rewards.