だい, で, てい
There is someone with a bow and a stick, wearing horns, going down a slide. What type of person do you imagine? I'd say someone who's an immature boy. That would be your younger brother.
Unfortunately, he goes down this slide too fast, bounces off the bottom, and then falls right on his stick. It goes through him, causing your younger brother to die (だい). That's right, he's dead (で) now.