It's time to grab your Trend Balls and send the ladies of Venus Island swimming, because that's the theme this time, not because you can actually make them swim.
The Boss asks Misaki and Fiona to pay him a visit, telling them a Rival Fest will be held during the festival this time around. Both girls are pumped and ready to win, as the boss hands them swimsuits that seem to be designed for competitive swimming...
The Trendy Gacha this time, as you might be able to guess, contains the Sunset Fish swimsuit for Misaki & Helena, and the Twilight Fish swimsuit for Fiona & Ayane.
Logging in during the event will get you Trend Balls, which are also one of the rewards for completing volleyball matches. You can redeem these for items in the event store, of course. However, there are also Trend Ball (Event Day Only)s which can only be redeemed the day that you get them! They reset at 7pm UTC every day, but can be used alongside the regular Trend Balls to redeem items in the store.
The main use of Trend Balls, however, is to take on strong opponents in volleyball matches. They increase your POW, TEC & STM for any girls participating, and starts the match with a max Tension Gauge.
The "Rival Festival ～ Youthful Swim ～" festival will run until 3rd of August 2021.
If you want to participate in this festival, unfortunately Dead or Alive Xtreme Venus Vacation is still only available in certain regions via Steam, and digital download in Japan.