In the second to last episode of the Soul Eater anime, Death the Kid connects all three Lines of Sanzu. According to the lore, the Lines of Sanzu only connect when a person is ready to become the next Grim Reaper. Since only one Grim Reaper can exist at a time, this usually means the current Reaper drops dead immediately. There came a crack in Lord Death's mask when Kid did it, but he survived.
Why, then, doesn't Lord Death die? Is it because Kid only unconsciously connected the lines?