Originally Posted by Unregistered

Can someone explain the Guest Party part in the event details, it says that they can be added to my party as helpers. How do I add them as helpers?

I'm pretty sure that's a plug-in for the event-gacha, which gives you an increased chance to pull those girls instead of other girls of the same rarity.

The underlined bit is important for all event gachas, by the way. The increased chance means that IF you pull a gold from an event gacha, that the chance to pull an event girl is greater than the chance of pulling one of the other available gold girls. But, the chance to pull some gold girl is still 6% as usual, and the chance to pull some rainbow girl is still 0.5% as usual.