It's fairly simple to explain. There was only one popsicle left. So Aqua, Namine, and Kairi decided to share it. But for the life of me I can't fathom why Link and Mario are there besides catching some rays on the beach. But DevianTart is really all the explanation needed.
The girls decide to share an ice cream, and the Roxas in Sora is making Sora freak out, since it's the last one. Mario and Link are on vacation from saving princesses, and they decide to go to Destiny Islands to chill. Sora was supposed to chill with them, but he's still freaking out about the ice cream.
If there was some kind of technology that turned our brains into represented images, this would probably be mine...
Clearly it is an insightful message about the near lack of high quality Aqua rule 34, which the creator decided to the need for more by making a picture of her, Namine, and Kairi sharing ice cream.
a group of women non-sensually share an ice cream because that's their only opportunity to have a presence in the kh series get rekt tetsuya nomura
But the two strongest and most interesting characters in the series are women. They even overshadow most of the male protagonists in how well put together they are. Terra is the only male character in the series with any depth at all, and even then Yen Sid, Eraqus, and Mickey (all of whom hold some title to show how much they are worth) are the only non-protagonist males who are treated like they have any real importance in the story as a whole.
Riku had depth, but then Dream Drop Distance happened. Now he's pretty much every protagonist in any shounen manga that's ever tried a little too hard to be "edgy." At least Terra still has several personal conflicts to overcome. As for Sora? He may as well be a faceless mook in a first person shooter.
It doesn't change the fact that Riku did have depth for most of the series, and potentially could when the next game releases... I didn't mention Sora for obvious reasons.