If you’re an anime-only, it’s advised you skip this prologue and just go straight to the first episode.
It’s perplexing why they chose this as Dededede’s opener considering this is definitely not what the actual meat of the story taste like, but I do understand the intention.
Most likely, the producers thought that adding moments before the ending would be a good way to build intrigue. For example, when I get spoiled on a story by a friend, it makes me highly critical of everything I see in the story from that point on, guessing if this would lead to the spoiled ending or that my friend had just mislead me. It keeps me intrigued. But for the case of Dededede, I don’t think it works well.
I think this prologue is just filled with exposition that just confuses and ultimately misleads the viewer’s expectations, turning them off from the show. It could work since as you follow the girls life, you get attached to them, so the mystery of the prologue will keep the viewers at the edge of their seat. But prologues are all about giving the general idea of what your story is going to be like, and this simply doesn’t do it’s job as a prologue.
The first episode already does a great job introducing the characters and the world they inhabit. It also gives the perfect general idea — a silly story that doesn’t shy away from tackling serious problems, or in other words, being ‘deep’.
In conclusion, the prologue is unecessary and it’s better to skip it, but if you did accidentally watch it or want to watch it, it’s also fine. It doesn’t spoil the entire ending, just moments before it.