Abbreviation for "Daredemo Daisuke", if you're weeb enough, you'd know this roughly translates to "
It doesn't matter who it is, I love them".
The "Hell" part of this term refers to the situation of being stuck essentially trying to simp to several individuals only to find it very demanding as most of their money goes missing due to the endless mount of merchandise. Not to mention most events don't match up to a their schedule, forcing someone in DD Hell to choose who's the better
option. When compared to someone who simps for just one or two people, the crater in their wallets and how well they slept should give a decent
description on who's stuck in DD Hell.
A very good example is someone who finds themselves falling into the vtuber
rabbit hole, vtubers are those anime girls playing a game. You saw at least once on your recommended yeah? They wind up watching an entire backlog of clips and streams and essentially get addicted to them, They basically have no preferences in each vtuber yet and try to watch all of them. This is where most begin, in DD Hell.