TAG (manga)

A 2003 Hentai Manga by Suehirogari.

Mizumo's life turns upside down when she stumbles upon one of her classmates running around naked at the college cultural fair. Quickly brainwashed and trapped playing a twisted game of tag where "it" is forced via hypnosis to stay completely naked until she tags the next girl, Mizumo has to deal with the dawning realization that she enjoyed her naked dash through town a lot more than she should have...

... and then the blackmail begins.

Tropes used in TAG (manga) include:

And I Must Scream: The primary focus of the manga, outside of the obvious -- once triggered, the only effect on the girls is that their bodies go on autopilot, removing their clothing right where they stand. They are left alone mentally -- any sensations they feel other than that are their own, the only long term effect being the fact that they cannot bring themselves to put clothing on or cover themselves in any way. This makes the game even more horrific -- there's no compulsion to play along or enjoy it, just the silent guarantee that they're trapped until they do.
Body Horror: Let's ignore the obvious one, and focus on the climax of the manga -- Mizumo discovering the fortune teller is a hermaphrodite with a foot long penis, at least, and is really happy to see her.
Covert Pervert: Chiyoko, who unlike the other girls, takes to the game and the sex acts right afterwards with aplomb. Consider that it took Mizumo several weeks to come to terms with her sexuality, and Chiyoko is openly joining in an orgy the same day.
Fanservice Cover: The cover has Mizumo very obviously nude, hidden only by a few twigs.
Freudian Excuse: It's heavily implied that the fortune teller is barren due to her nature as a hermaphrodite, which the girls suspect is why she enjoys tormenting the girls so much.
Market-Based Title: The actual act in Japan is called "Baton Touch" -- touching base with your replacement before you move on to a new job or leave work for the day. However, it's close enough to the children's game that they went with the simple title Tag.
Mind Control: The various girls have all been brainwashed to compulsively follow the same rules of the game -- that is, whoever's "it" can't wear clothes, and they know they're "it" when someone else who is in on the game kisses them. They have also been given backdoor commands that the fortune teller can use in a pinch -- for example, when Chiyoko isn't home, the fortune teller aborts the game for Mizumo's safety. At the climax of the second to last chapter, she remotely triggers both Yuri and Mizumo and leaves them to try and beat each other to Chiyoko.
More Than Mind Control: ~~Mizumo~~ The four girls might have been brainwashed to start the game, but by the end they're all enjoying it, but each with varying willingness to admit it. Yuri claims to hate it (but is still fantasizing about it), Chiyoko plays coy, Moriyama is openly accepting of her exhibitionism, and as the last page shows, Mizumo is streaking at night on her own.
Nightmare Fuel: Imagine the setup of the series: You're at work. You look up, and a terrified nude woman is running up to you. She kisses you before you can stop her, apologizes, and runs off. Seconds later, your hands start ripping your clothes off without your input, ignoring your desperate attempts to stop. Seconds later, you discover you can't put them back on -- no matter how hard you try, your hands just won't move to do it. Minutes later, just as the panic really starts to set in, you're contacted by a group of strangers who tell you flat out -- you're going to have to get across town, without putting anything on, and forcibly kiss a complete stranger, which will then make them go through the same thing. And until you manage to kiss said stranger, you'll stay naked. Forever.
The Nudifier: A Mind Control variant -- the girls are all brainwashed to have the rules of the game embedded in their subconscious. If they're kissed by a nude woman in public, they'll strip naked and stay that way against their will until they can pass on the condition to someone else.
People Puppets: ... Meets The Nudifier. The affected victims are left completely alone, as long as they don't encounter the Trigger Phrase -- that is, being kissed by a nude woman. Upon getting kissed, they immediately strip against their will, and cannot touch clothing again until they kiss the next person in line.
Oh Crap: A non-verbal version, when Mizumo finally realizes where she has heard the name of the girl she met during gym class before. It's Chiyoko Naruai, the girl she was supposed to tag during her turn as "it" way back in chapter 2. This comes to her just as the two of them see Yuri having semi-consensual sex on the roof of another building with the same men that made her have sex on the same roof, making her realize that a. The "game" is afoot around her, b. Chiyoko must have been brainwashed as well (since she was a target of the game), and c. No one's done anything with her yet, meaning that the fortune teller must be plotting something. She's right on all 3 accounts, but warning Chiyoko doesn't work.
The End - or Is It?/Sequel Hook: The ending has all of the girls thinking the "game" is over, only to watch in horrified fascination as a random nude girl rushes into Mizumo's workplace, kissing another patron, then running away as said patron starts to strip. The final pages suggest that none of the girls are truly free of the hypnotic suggestions (or at least the events have warped them somewhat), and that Mizumo has started streaking on her own at night, no coercion required.
Sadistic Choice: In the final chapters, Yuri and Mizumo are both triggered from remote over a cellphone, leaving them trapped naked at their college, with the condition being that one of them will be allowed to stop playing the game, if they can find Chiyoko. Of course, the other one (and Chiyoko) will be trapped in the nude for the foreseeable future and still be considered still part of the game from now on. Mizumo takes a third option, voluntarily giving Chiyoko to Yuri because Mizumo has realized she doesn't really mind it all that much anymore, and Yuri is genuinely upset.
Sempai Kohai: A chain example -- Moriyama is older, wiser, and more experienced than Mizumo, and happens to be her senior. By the end of the series, Mizumo (a Sophomore/Junior) is acting out the same role for Chiyoko (a freshman), who is so innocent it almost hurts. (Of course, then she willingly starts having sex to "help" Mizumo, no brainwashing required.)
Tempting Fate: The events of the series started because Mizumo mocked the fortune teller within earshot to Yuri. The fortune teller then lured Mizumo into her room and hypnotized her, putting her into the game. (Yuri was hypnotized right afterwards, when she went in to check on Mizumo.)
The Virus: The "game" is being spread to any attractive girls the fortune teller can get alone long enough to brainwash. There's only one "it" at a time (usually) but it's passed around like a curse or infection.
Voice with an Internet Connection: While the fortune teller presumably doesn't have internet access, she's gotten a harem of men helping her out by watching the girls streaking across town. She gives the girls phones repeatedly throughout the series, which she uses to command them (and in some cases, trigger post hypnotic suggestions).
Xanatos Roulette: The fortune teller, who is randomly brainwashing people around town to make them participants in the game. When Chiyoko isn't home, instead of leaving Mizumo to wait around, she intervenes, temporarily breaking the game, but only because it would cause Paranoia Fuel in Mizumo the next day, which causes her to contact Moriyama to figure out what's going on and sends her falling off the exhibitionist's slippery slope. It's insinuated that she can keep all this up because the men involved are all assisting her in watching the girls during the games.
Zen Survivor/Trickster Mentor: Moriyama, who is pulled in via the fortune teller to help "train" Mizumo when she randomly walks up to leer at her exposing herself to a building Moriyama was in. Previously having gone through the same situation only to come to terms with her own exhibitionism after the fact, she turns out to be just as bad as the fortune teller -- making Mizumo go into an adult toy store while essentially naked, tricking her into peeing in front of dozens, and then dragging her to a love hotel to use the toys she made Mizumo buy.