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The library was quiet that afternoon, the tall shelves of leather-bound books casting long shadows across the polished wooden floor. Dust motes danced lazily in the golden light. Normally, it was a place for study, relaxation and reflection, not chaos, but I suppose in the House of Lamentation, peace never stays for long.
MC settled into the couch, curling a hand around her tea, feeling the soft warmth seep into her palms. This is going to be… interesting, she thought.
When Diavolo suggested the exchange programme include a “comprehensive understanding of human biology”, Lucifer assumed MC would handle it with poise and dignity.
MC assumed Lucifer was joking.
Somehow, Mammon ended up at the end of the room, standing in front of a whiteboard, a marker in one hand, and entirely too much confidence radiating off him. MC, comfortably sprawled on the couch, decided not to interfere—yet. She was curious and very amused. Maybe even a little impressed by Mammon’s bravery. Mostly, though, she was enjoying the chaos before it even began.
“Okay!” Mammon said, slamming the marker against the board for dramatic effect. “Listen up, everybody! Today, I, The Great Mammon, will teach you about… uh… humans!”
He paused, scanning the room. Beel was sitting cross-legged on the floor, looking at him with hopeful eyes. Levi was already squinting at the whiteboard, blushing. Asmo was hovering nearby, playing with his hair. Belphie was slouched on the couch opposite MC, half-asleep but suspiciously attentive. Satan was leaning against the wall, arms crossed, waiting for someone to make a mistake. Lucifer’s expression was deathly calm, but his eyes screamed murder.
MC watched it all quietly, a small smirk on her face. He really believes he can do this. She sipped her tea, thinking how ridiculous it was that Mammon, of all demons, was about to teach human biology… and how thoroughly she intended to enjoy it.
Mammon grinned, clearly oblivious. “Alright, so first things first: humans have… parts!”
He drew a stick figure with three knees, two arms, and a head that seemed to be on backwards. “This is a human! Probably…”
Lucifer glared at him.
“Don’t look at me like that, Lucifer. I’m explainin’ it in simple terms!”
MC was struggling to control her facial expression.
“Those are not the correct proportions,” Satan muttered, his voice laced with academic contempt.
“Groundbreaking,” MC said, trying to stifle a laugh as she covered her mouth with her hand.
Mammon’s grin widened. “SEE? MC believes in me!”
Levi wheezed loudly. “Oh my Diavolo… that is horrifying.”
“Mammon, be serious,” Lucifer interjected, pinching the bridge of his nose. “And show some restraint. If you value your life.”
“Relax, Lucifer,” Mammon said, ignoring him entirely. “We’re just getting started. Now, humans reproduce—uh, obviously. Bees help or something. No, wait, that’s not right… Was it birds? Anyway, here’s where it gets… complicated.”
He drew a heart and an arrow pointing vaguely towards the stick figure’s… middle.
MC bit her lip, trying not to burst into laughter. He’s going to make everyone lose their minds… and it’s hilarious. “Mammon… you’re doing… amazing.”
“THANK YOU! Finally, someone recognises true genius!” Mammon beamed.
Asmo clapped politely, leaning forward. “Darling, if you allow me, I can explain the… advanced techniques~ It’s really quite an art form.”
“Please don’t,” Levi groaned, facepalming. “No. Just… no.”
Beel tilted his head. “Wait… so if humans have… that… does that mean all humans have the same… stuff? Or are there variations? Like… what if someone’s… missing one part?”
Mammon blinked. “Well… uh… maybe they just… get a redo?”
Lucifer’s face went entirely still, like the calm before a storm.
Satan chimed in from the other side of the room. “Mammon, you’re about to cause irreversible psychological damage.”
Belphie mumbled something in his sleep that sounded suspiciously like, “What an idiot.”
Levi was frantically flipping through a book. “Okay, okay, we need to define the reproductive system in precise anatomical terms. Start with—”
“STOP!” Mammon shouted. “Listen to ya brother! I’ve got this under control! Humans are simple. They’ve got parts. And… stuff. That’s it!”
MC’s shoulders shook as she leaned back, enjoying the spectacle. I can’t believe this is happening. “I think you’re nailing it, Mams.”
Satan sighed. “I can’t. I simply can’t. This is physically painful to witness.”
Mammon ignored him. “Now, humans sometimes… uh… kiss? And then, boom—baby?” He gestured wildly at the stick figure, which now had a second head for no apparent reason.
Oh my good Diavolo. MC wiped the tears from her eyes and tried not to burst out laughing.
“Incorrect,” Levi yelled. “Completely wrong. That is—oh Diavolo, the proportions are—no. Stop.”
Asmo swooned dramatically. “I feel like this could be… so romantic! Mammon, darling, you’re really inspiring.”
Beel raised a hand. “So… wait… if two humans kiss, that’s how babies are made?”
“Sometimes,” Mammon said confidently. “Depends on if they… yeah. Whatever. Science!”
Lucifer sighed so loudly it echoed off the walls. “This entire exercise is a failure. Forgive me, Lord Diavolo.”
MC covered her face, shaking with laughter. She could intervene—she really could—but honestly? Why ruin the fun? Mammon was glowing with pride, Levi was frantically comparing Mammon’s diagrams to his book, and the others were either confused or enjoying the show. It was peak chaos.
“Wait!” Beel interjected again. “So… what about… that, uh, female… timing thing? There’s like… a schedule or something, right?”
“What?” Mammon blinked. “Schedule?”
“Yes, Mammon! Biology has rules~” Asmo sang.
“Relax, nerds,” Mammon said. “I said humans are simple! There are no rules. That’s the whole point!”
Belphie’s voice drifted from the couch. “I like this dream.”
Lucifer groaned. “I cannot believe I agreed to allow this.”
MC laughed, shaking her head. This is ridiculous. I love every second. “You’re… doing great, Mammon.”
“THANK YOU! FINALLY! Someone gets it!” Mammon pumped his fists.
By now, the stick figure had multiple extra arms, a suspiciously large head, and what might have been wings—though Mammon insisted they were “optional accessories”.
“Optional accessories?” Satan repeated flatly.
Levi continued, “We are discussing human biology, not cosplay!”
“Details!” Mammon waved it off. “Minor details. Humans don’t care!”
As the chaos escalated, MC finally decided to step in just to add fuel to the fire.
“Actually,” she said sweetly, leaning forward, eyes sparkling with mischief, “I think you’re missing a very important detail.”
Mammon’s eyes lit up. “Oh! Yeah! What is it?!”
MC smiled innocently. “What about female biology? You haven’t mentioned periods yet, Mammon.”
Mammon froze. “Wha—periods? You mean… like, homework? No, wait… that’s different.”
Levi squealed, burying his face in his hands. “Oh no, no, no… this is… horrifying. Absolutely horrifying.”
Satan gave a sadistic smirk. “Go ahead, Mammon. Explain it… as best you can.”
Beel tilted his head. “Wait… what’s a period? Is it… dangerous?”
“No!” MC chuckled. “It’s… normal. Every month, the body—uh—clears itself out. Blood. Hormones. Stuff like that.”
Mammon blinked. “Wait… humans… bleed?”
“Yes, females do,” MC said, smiling innocently. “But it’s normal. Totally normal.”
Mammon’s eyes went wide. “Oh… oh! So, like… humans are… uh… tricky!” He waved his arms dramatically. “See? I knew humans had secrets! Secrets everywhere!”
Asmo floated closer, eyes sparkling. “Darling, this is so fascinating! It’s like a romantic tragedy—biological edition!”
Levi squeaked. “Romantic… tragedy… nonononono.”
Lucifer groaned. “I refuse to witness this.”
Belphie mumbled, half-asleep, “Hmm… biology’s complicated.”
Beel raised a hand. “So… does it hurt? Is it dangerous? Should we… like… help humans?”
MC chuckled. “Mostly, it’s manageable. We usually get products—pads, tampons, chocolate.”
Mammon scribbled something incomprehensible on the whiteboard. “Chocolate… got it. Humans survive because… chocolate! Perfect logic.”
Levi flailed. “No, no, no, it’s not logic—!”
Satan muttered, “We should never have let this idiot teach.”
Asmo twirled dramatically. “I volunteer to teach ‘comfort techniques~.’ Very hands-on.”
Lucifer pinched the bridge of his nose. “Oh, Diavolo, save my sanity.”
MC leaned back, smirking. PFFTTTT—HAHAHA. “You’re doing great, Mammon.”
“SEE?! MC APPROVES!” Mammon shouted, throwing the marker into the air like a trophy.
The lecture continued. Mammon drew increasingly absurd stick figures, each “anatomical” correction more chaotic than the last. Levi repeatedly tried to clarify terminology, but Mammon waved him off. Beel asked several highly practical—but awkward—questions. Asmo continued his unsolicited “advanced demonstrations”. Belphie occasionally muttered half-asleep comments that were somehow still on topic.
By the end, Lucifer had a full-blown migraine, Satan had confiscated all the markers, Levi had barricaded himself in the corner, Asmo was planning a deluxe anatomy seminar, and Beel had learned more than he probably needed to know.
Mammon, exhausted but proud, grinned at MC. “I’m… the best teacher ever, right?!”
MC smiled sweetly, stretching on the couch. “You really are, Mammon. You did great.”
Lucifer groaned, thinking about how he was going to tell Diavolo what had transpired.
MC sipped her tea, watching seven demons argue, explain, and utterly fail at human biology. After all, if the lesson was going to be a disaster, she would enjoy every single second of it.