Actions

Work Header

Rating:
Archive Warning:
Category:
Fandom:
Relationships:
Characters:
Additional Tags:
Language:
English
Series:
Part 10 of Beetles' Forcemasc Fics
Stats:
Published:
2026-06-11
Updated:
2026-07-23
Words:
10,618
Chapters:
6/?
Comments:
2
Kudos:
47
Bookmarks:
3
Hits:
1,394

Men are Beasts

Summary:

Dazai, boss of the Port Mafia, finds a little orphan girl and molds her into the perfect assassin: the White Reaper, Atsushi Nakajima. Now transitioned to a man, Atsushi is hard to control. Inside, his tiger rages, and he struggles with the guilt of what he's done and the person he really wants to be.He really shouldn't worry about that, though. Dazai will teach him everything.

Or, the BSD Beast forcemasc fic

Notes:

A repost of sorts from my oneshot collection, with a continuation i'm hoping to publish super soon, like I'm writing it right now

expect for this to be similar to my Akutagawa forcemasc fic, but with mafia Atsushi instead!

Chapter Text

Atsushi sat very still as Dazai cut his long white hair short, the concrete floor cold against his naked thighs. Even without a mirror, he could tell that the cut was not good – it was too choppy, nothing like the kind of hairstyle a respectable man would have.

But then, Atsushi considered, he was not a respectable man, was he?

His bare neck felt cold as Dazai took the scissors away, then whispered in his ear, “Very nice.”

…….

 

Dazai was the boss of the Port Mafia, the most feared criminal organization in Yokohama’s underworld, a cold, pitiless man known as a demon and a monster. Despite this, he had taken in Atsushi, rescued him from the miserable state he’d been in – and he’d made him into a new person.

“You’re really a boy, aren’t you?” He’d said back then, his one visible eye gazing at Atsushi intently.

“No – I mean, I don’t know. Am I?”

“You are. I can tell. I’m going to refer to you as a boy from now on, understand? Don’t ever call yourself a girl again.”

And Atsushi hadn’t. Now, he automatically thought of himself as male, thanks to Dazai’s constant training. His hair was short, he dressed only in male clothing, and his chest was bound tightly to prevent a hint of feminine softness.

Then came the shots. Dazai injected him with testosterone, which was meant to make him even more masculine. Atsushi could feel his previously high voice getting lower and scratchier, his body changing. 

 

“Get up on the chair, all right, Atsushi?” Dazai smiled and gestured to the medical office. “I need to examine you.” Dazai always insisted on doing Atsushi’s checkups himself, claiming he was the one who was responsible for him. Atsushi didn’t mind. He wasn’t allowed to protest.

“Let’s get those pants off,” Dazai said, swiftly leaving Atsushi’s lower half bare on the table, his top half clad in only a thin shirt and his binder. “First, let’s do your shot.”

Atsushi was used to the prick by now, and even more used to the way Dazai stroked his legs lovingly before doing it.

All right, now let’s get your legs spread.” Dazai grabbed Atsushi’s ankles and strapped his feet into stirrups; he’d started doing that since Atsushi had struggled too much one time. Atsushi covered his face with his hands.

“Please don’t take too long,” he murmured. “It’s embarrassing."

“There’s nothing embarrassing about your body,” Dazai reassured him. “I just need to see how you’re developing.”

He then turned his attention down to Atsushi’s crotch, examining the swollen t dick jutting up from its hood. He turned it back and forth with his fingers, ignoring the way Atsushi twitched and gasped at each caress. He felt hot and strange. Every time Dazai did this, his cock was bigger and more sensitive.

“It’s coming along nicely,” Dazai said. “I can tell the increased dose is paying off. How has your hole been? Testosterone can cause dryness in the vagina or even atrophy, if you’re not careful.”

“I’m not sure,” Atsushi breathed, still covering his face. He was so hard, and Dazai kept touching his dick then taking his hand away, almost as if he was teasing him.

“I had better check, just to be sure,” Dazai said, and slipped two fingers into Atsushi’s hole.

“Uuhhh,” Atsushi moaned a little, as Dazai began pumping his fingers in and out. He clenched down, feeling as if he was going mad.

“Seems like there’s a good amount of lubrication,” Dazai said. “But we can’t be sure unless we put something a bit bigger in there. You might be fine with just a finger or two, but unable to handle a dick. We need to check right away.”

Atsushi couldn’t stifle another moan. He could no longer stand it as Dazai stepped away, reaching down, rubbing and fondling his achingly hard cock. It felt so good to finally touch it, and he felt himself close to orgasm when Dazai returned and grabbed his hand.

“What have I told you about touching yourself during examinations?” He scolded, then restrained Atsushi’s wrists to the arms of the chair. “Really, Atsushi. Just stay still, the sooner I’m done with this, the sooner you can get out of this chair and jerk off to your hearts content.”

“But Dazai,” Atsushi began to protest, only to have his mouth gagged.

“No talking. You’ll just distract me.”

Atsushi squirmed as he felt the slick head of a dildo pressing into his hole. It was big, he could tell, and he shook his head, trying to communicate that he didn’t want that shoved inside him, but Dazai ignored him. He’d hooked the dildo to his harness, positioning it against Atsushi’s slick hole and bumping it against his neglected cock, tormenting it further.

Atsushi didn’t like it when his front hole was penetrated. He preferred to stimulate his dick instead, and Dazai knew this.

“It might be difficult for you to take the whole thing,” Dazai said, “But we need to make sure nothing is too dry or tight, okay? This is all for your own good.”

Atsushi could only watch as Dazai lined his cock up to his hole and rammed it inside. He cried out in pain, devolving into groans of pleasure wrung from him with every thrust that stimulated his dick or g-spot. It hurt, the dildo was too big, it filled him up too much…and it hit him in all the right ways, making him moan and drool around the gag as his eyes rolled back.

“You’re doing amazing,” Dazai praised as he thrust back and forth in quick, sudden bursts. “I think your hole is perfectly healthy."

Atsushi could only gurgle slightly in response. He was so close to cumming, so close he could feel it. He needed the release more than anything. There was nothing in the world worth thinking about...only Dazai’s big dick and cumming.

Abruptly, Dazai pulled out, admiring how wet his cock was. “Excellent,” he said. “I think that concludes the exam, don’t you?”

Atsushi sobbed, thrusting his hips forward. He’d been so close, and now he felt empty, his cock twitching.

“What’s wrong?” Dazai smiled, leaning over him. “What do you want, Atsushi?”

He removed the gag. “I want to cum, please,” Atsushi moaned. “Please let me, sir.”

“All right.” Dazai gripped Atsushi’s cock and began to pump it, harder and harder until Atsushi came, squirting fluid over Dazai’s face and hands. He cried, feeling humiliated and tired.

“What a lustful young man you’re turning out to be,” Dazai said, undoing the restraints on Atsushi’s ankles and wrists. “Makes me glad that I made you.”