A new craze is sweeping society, the Slave Control Method or "SCM". It's a gumshield which allows people to duel, using any competition they like, with the winner gaining psychological control over the loser.
Control here means almost anything, though there are certain limits. Still, it will let you manipulate people's actions, which has a range of uses, though the most obvious one people seem to think of is usually sex. Funnily enough though, this isn't actually porn. Instead, it's impressive horror.
The gumshield sends signals to people's brains, and makes them feel the obligation of defeat, such that they are driven to obey orders, creating slave and master bonds.
Trouble is, this defeat takes a range of forms, depending on how honourably they play the game. See, it's entirely possible for people to cheat. Such as by lying, having a ringer, winning the duel before it starts or finding a more traditional way to cheat. This is the preferred tactic of Eia, who became involved in the "scene" after her friend's boyfriend suddenly vanished under suspicious circumstances.
There's a range of factions forming, but the likely overall villain is Ryuuou, who is slowly acquiring an increasing number of slaves, to an unknown end. However, as some absolutely madman just let these out into the free market, anyone is able to challenge people with an SCM. It's possible to turn down a duel, but only if you're not tricked into one.
The duels have been a range of things, but tend to be something that are traditionally low stakes. Trivia contests, thumb counting, a bit of pachinko. It could potentially suffer the usual problems involved in shows where those games are the focus (looking at you, sports anime), but here there's more than enough tension due to the wider challenge involved in staying a free agent.
It's a very violent show, both within the context of duels and forcing people to do things they don't like (guy having to punch himself in the face was brutal) but it really sets the tone for the horror.
There is a bit of a problem with the central premise in that you'd have to be insane to go along with any of it, but that's mostly skimmed over, and the series clips along fast enough that you won't necessarily worry about it.
The one other downside to it is that more or less the entire cast are unlikable. You're not going to be cheering when someone loses until probably the last episode or two of this. Still, that is part of the overall nature of the programme. One I'll keep watching.