It was obligatory wasn’t it? They also put Merry into a “sukumizu”; they really love making her wear costumes.
They’re at the beach! So expect all the usual Japanese beach antics such as smashing watermelons and having college students in Speedos picking up underage girls. What fun!
Plot wise, we meet a new character: Treesa. I say that we meet her and that she’s a new character but Treesa was the demon that killed Serio (that weak plant thing). In a nutshell, Treesa is the demon that has been robbing humans of their dreams and she’s also in alliance with the “Lighthouse”. It’s ironic because Merry was just recently doing that as well. Treesa is simply taking over the position.
Anyways, this beach episode is used primarily to cheer Merry up from her melancholic state. It’s not the most intriguing of watches.
So, there isn’t much to say as everything has already been said.
It’s a rather common trope for a protagonist to have a depressed streak. There’s always an episode dedicated to their cheering up, this just happens to be the one. Normally, in exchange for the lack of exposition, there’s an ample amount of fan service but not so much in Yumekui Merry. There is however, a subtle focus on character development in place of that. Small things like Kawanami having regular pupils, instead of those X’s that would denote her being a dream demon, or her asking about Isana’s painting dream makes me think that they want to slowly increase her importance in the story She also seems to have blue eyes, I’m fairly certain that her eyes were brown before.
Another trait that is common within these filler episodes would be flashbacks. There are a few, involving Play and how she told off Merry. This episode is quite random in that sense. There’s a decent amount of development going on but it’s spread thin between several characters. Even Saki had a moment of glory as Akiyanagi (whom I still think is a dream demon) helped her from those trying to pick her up. She’s only been seen a couple times in the anime!
Watch this simply to watch it. There isn’t a ton of substance that is monumental to the plot.