Eren is ambushed late at night as he's about to stumble into his bed in the basement. In hindsight, Hange probably picked that exact moment because she knew Eren would agree to anything if he would just be allowed to get to his own bed.
"Great! I'm only lending you the first three so you can get a start," Hange told him cheerfully as she skipped away. "You're going to have to buy the rest on your own!"
Out of random curiosity, he flips open the first one right before sleeping, just so he knows what Hange wants him to do. Is it another one of her experiments? Most likel-
"Oh, Commander," Rivaille says, swooning and collapsing into Irvin's finely muscled arms. "My passionate lust for you cannot be contained any longer; it is a raging fire in my heart that somehow quells even the unending fury I feel about the terrible Giants. I cannot contain it any longer, Commander, please take me!"
Eren's traumatized scream echoes throughout the whole castle.
"It's tradition," Gunter says, when Eren embarrassedly asks the next day. "Every time a book comes out before a big mission, everyone in the Scouting Legion goes to read it. I mean, well, it's sort of like good luck." The older man scratches the back of his neck. "Usually, when it does happen, we get less casualties on the trip, so nobody wants to break it." He lowers his voice, eyes darting nervously around the room. "And, well... you can't say that they aren't... entertaining."
"Don't worry, Eren!" Petra says. "It was, well, pretty embarrassing at first. Especially the reading out loud part, but after one or two times you-"
"Oh, uh, nobody told you?" Petra glances around to the rest of the squad, all of whom shrug. "Well, the newest member of the Scouting Legion has to read aloud the first chapter that has sex in it. Which is basically all of them. It's like an initiation." Most likely recalling her own experience, Petra blushes lightly.
"Don't worry," Auruo says, clapping Eren on the shoulder when he turns a fascinating shade of green-purple. "Everyone's gonna be drunk, it'll be fine. And you don't even have to read the Comman- sorry, "Irvin" and "Rivaille's" parts, the Commander reads his own parts and Hange reads the corporal's. You just have to be the narrator."
"Like Petra said, initiation," Erd says. "It's only one chapter, after all. And besides, didn't you say your friends have joined the Legion? They're going to have to read too."
Eren suddenly pictures Mikasa reading one of the scenes out loud. Or, for that matter, someone with Connie's maturity level. Or, heaven forbid, Christa.
"Maria save me," Eren says.
"Oh, come on, Eren!" Hange says, dragging him to the bookstore. "You haven't even finished reading the first three, how are you supposed to catch up with the rest of the story? Don't worry," she adds, noticing the mildly paranoid look that Eren gives their surroundings, "I got the ok from the Commander to bring you out. Just for today, so we can get you ready for tomorrow night!"
"...Jean?" Please, Sina, no.
"What are you doing here?" Jean asks, frowning in confusion.
"We're stocking up on supplies!" Hange answers for him, enthusiastically yanking his arm. "Don't mind us!"
"Supplies in the book store?" Jean asks, but now it is only to the opposite wall- both Hange and Eren have disappeared into said store. He stands, puzzled for a few moments, before deciding that actually, yes, he is very curious as to why they've allowed Eren out within Wall Sina.
He stealthily- or tries to, at any rate- follows them inside.
"Here we are!" Hange says, stopping in front of a bookshelf. "The newest one is the eleventh; I've managed to persuade Levi to give you the rest of the day off so you can catch up on the rest. Don't bother reading the eleventh one yet, though; you can read it yourself during dinner tonight! And don't even think about spoiling the surprise for yourself- it's more fun that way."
"Fun," Eren echoes faintly.
"Exactly! That's the spirit, Eren!" Hange piles books onto his arms. "Now come one, let's pay for these so you can get started." She happily walks over to the front to pay, Eren following mindlessly behind her with a look of pure horror on his face. Jean frowns, and leans just the slightest bit further forward in order to catch a glimpse of the spines of the books-
'Commander and Corporal 4: Lost in the Mountains of Ecstasy'
'Commander and Corporal 5: The Mourning Woods'
'Commander and Corporal 6: Only a Little Death'
Jean blinks. And blinks. And, very slowly, he decides that no, he does not want to know.
Eren wants to hide so desperately, but the Commander and Hange have already stood up with the copy of the newest books in their hands, 'Humanity's Largest Soldier'. Has he prayed to Rose yet? He doesn't think so. Please Rose, save him.
Not that praying does any good.
"I'll read Levi's part since he doesn't want to!" Hange declares. Levi gives her a glare. "Oh, sorry, I'll read 'Rivaille's parts. Eren, you start!"
Eren doesn't want to. He really doesn't want to. Levi gives him a stare.
Eren swallows, and resolves to at least not look Mikasa or Armin or any one of the members of 104th in the face. At least let him get out of this with some dignity intact. He takes a breath and begins.
"It was a dark and stormy night when Corporal Le-Rivaille had finally stumbled back into the barracks. He was dripping wet with cold rain, the wetness pinning his shirt to his body, highlighting every toned muscle and every curve of his fit, athletic body. It was late enough that nobody should be awake, and indeed, majority of the Recon Corps were asleep. Even Petrina, the witchy blonde hussy-" He chokes, and Petra lets out an alcohol-fueled cry of, "I'm not a hussy!"
Auruo pats her on the shoulder in a mockery of comfort. "Issokay, Petra. We know you're just a 'heathen jealous floozy', not a hussy." Commander and Corporal 9, chapter 18. Maria, why does he remember this? He doesn't want to remember this.
Petra gives Auruo the dirtiest look possible, and only because she is already halfway to being utterly and totally smashed, she picks up her bread knife and makes very loud, visceral threats about his continued possession of a penis. Gerger begins to cheer her on, holding tight to his bottle of Vine.
"Yeager, continue," Levi says, not even batting an eyelash at the commotion.
"Yes, sir," Eren mumbles under his breath, already resigned to his fate. "Even Petrina, the witchy blonde hussy, had fallen asleep, too tired to wait up for him any longer. If only she hadn't fallen asleep in his own bed. Now where could he sleep?" And then the narration ends for a bit, and Eren is so thankful that he doesn't even notice Erwin clearing his throat to begin his part.
"Rivaille." Oh gods, he's using the voice he uses when he shouts orders to the scouts. Oh gods, he's using the shouty-order-voice and Eren is never going to be able to take him seriously on a mission ever again what has his life become. "Why have you spent the night away? Where were you? Did you not think that your absence would worry me so?"
"I am sorry, my dear." Hange lowers the pitch of her voice to read Rivaille's dialogue- it just makes her sound like a choking midget. "It was urgent business that I had to attend to," she continues in a far too overly-serious tone.
The sudden glare that is sent his way by Levi reminds Eren that it's his turn again. "Irvin did not need to know of the ways that he spent his time in the slums of Wall Rose, his b-beloved dear heart did not need to know of the crimson stains from hundreds of lives that marked his hands. What he did in town was not for Commander Irvin Smith to know, and certainly not something that the commander of the Recon Corps should ever be associated with."
"Come to bed, my darling," Erwin said. "But you should take off your clothes first. You can't sleep when your clothes are so wet."
"Irvin's eyes ran over every inch of Rivaille's body as his lover obeyed and stripped off his shirt." Eren is dead, he didn't really manage to survive being swallowed by that titan. He's dead and this is his eternal damnation. That is the only explanation for this hell. "His sapphire eyes were glowing with a primal, bestial hunger a-and he could feel his..." Eren chokes yet again.
"Keep reading, Yeager," Levi commands. Hange glances down at her own copy of her novel and sniggers.
"It's not even the worst we've found," she says. "Just do it."
"It would be a shame if we had to halt our tradition for such a small matter," Erwin says mildly. Everyone in the mess hall looks to Eren expectantly. He thinks that he can even see Mikasa leaning forward in her seat a little.
Eren steadfastly does not whimper. Okay, maybe just a little. "...he could feel his m-m-" He takes a deep breath. "-manly p-poker pressing against the soft cotton of his trousers as his gaze lingered on Rivaille's- ...rigid tiny nipples..." His face is so red and burning in sheer mortification by now that you could probably use it to cook a meal. "At long last Rivaille had finished removing his clothing, stripping down to only his undergarments, before slipping into the sheets next to Irvin. The blond man noted that Rivaille himself was half-erect; obviously the other man had felt the sensual slide of fabric over his chest and Irvin's own lustful gaze."
"Should we?" Erwin asked, entirely deadpan.
"Yes," Hange said, desperately trying not to cackle at Eren's obvious suffering.
Eren buries his face in his hands.
"Read," Levi commands. "We don't have all night."
"Irvin's large manly hands easily pulled away Rivaille's cotton underpants, leaving the smaller man completely nude under the thin blanket. Rivaille's own... throbbing flesh club was now hard and completely erect. As Irvin took it in his hand, he thought it was larger than it was last time.
"In a well practiced motion, Irvin rose to his knees and gently turned Rivaille's body around-" Eren stops, he has to. He can't. He lets the book drop and his hand fall, allowing his head to slam onto the wooden table with a loud thump. Maybe if he hits his head hard enough, all his memory of this event will fade away and he'll be fine in the morning.
Levi's glare does nothing to rouse him. Hange checks him over, and says with a sigh, "He's out. I don't think we can make him read any more without breaking him."
"A shame," Erwin says. He picks up the fallen copy, looking around for the newer recruits. "We'll have to get somebody else to read this, I suppose. We can't just stop in the middle, of course." More than half the room is already drunk; it's not like they'll be listening in, but then again, tradition is tradition.
Levi snatches the book from Ewrin, eyes scanning the room until he finds the person he's looking for. "Ackerman," he says, pausing only just long enough for Mikasa to look up before tossing the book at her. "You continue from where he left off."
Mikasa catches the novel easily, sending Levi a small glare. He doesn't back down- and it's only after Armin clears his throat that Mikasa turns her gaze away from him to open the novel. She quickly finds the page that Eren stopped at- the second page, of 183- and blinks once. And then, absolutely deadpan, she reads, "-and with smooth, swift movement he plunges his hot swollen rod of manhood deep within Rivaille. He feels the other man undulating underneath him, Rivaille's jiggling globes of flesh bouncing against his thighs-"
She pauses. Jean looks like he wants to claw his ears out.
"What is it now?" Levi grumbles. "Just read the damn book."
Mikasa lowers the book and looks up, her gaze exactly meeting the Corporal's. "Is this how babies are made?" she asks, utterly serious.
In the middle of the chaos her question causes, nobody notices Armin pocketing the, by now, long-forgotten novel. He smiles. "I've been waiting for this one to come out for months!"