[Umm... Content warning?]

      "Oh hello there, sweet brother of mine!" Ruby was giddy, giggling as she slowly knocked on the open door to enter.

      "What do you want?" A groan came out of my mouth. I was happy that my obnoxiously loud 'team' had headed out. Only for this one to come in.

       "You know. Just wanting to hang around my  favorite family member."

       "Ruby, as long as your father despises me. I don't count as one." I'm not even sure we're blood related.

       "Oh Don't be like that! We grew up together. I'm sure we have a bond like no other!"

      Her innocent voice skipping closer until she was directly behind me. Her hands went directly into massaging my shoulder. I could hear a soft inhale from her as if she was bracing herself for something.

    "You know..." Ruby trailed her voice up. "I may or may not have heard that Team (Y/N) had some... Weapon upgrades. And I was wondering—"

      "No." I answered before she could even finish.

      "What? Oh come on, I didn't even finish!" She shouted directly near my ear.

     "You want me to hook you up with my 'secret weapon dealer'? Sorry, but I don't think I can just send off pipsqueaks like you to that part of town."

      "Ugh... Yang will come with me!"

      "Did she say she will?"

      "... No she said the same thing you did." The girl hanged her head in defeat.

     "Comeee onnn... Pleassseee. I'd love Crescent Rose to be as versatile as your DeusExMachina! Just one upgrade and I'll never ask for anything again!"

       "Ruby Rose..."

       "Yes, (Y/N)?"

       "Give it up."

       "Now now (L/N). Let's talk this over first."

       "No."

       "Whyyyy?" Little Red turned chibier and chibier by each reaction. I wondered how far she'd go until she'd eventually shrink small enough to be ignorable. But it's not like I can do that.

       "Alright let's have a match then." I sighed. Well it won't be anything like one though.

       I stood up and went towards my desk. “You’re making a unilateral request, Ruby. In gaming terms, it’s not a match between players. You’re playing against the house.”

       Her expression shifted. As if she lit up. Was she equipped with some sort of vector-motion sensor that would respond automatically at a mention of a match.

       "Hehe. Deal! I see I have to prove myself to be as edgy enough like you?" She assented. "Just give me the rules then, I'll handle it no problem."

         Hmph. She's too naive. It takes a lot for me to get worried for someone. She was it.

        I'd have to teach her a lesson.  She asked me what rules. So its up to me. But it shouldn't be impossible for her to complete. It has to be a feasible Challange—A seemingly fair setup.

       But its hard to think of something doable. Yet still challenging for her. Admittedly, when it came to skill, she has her perks. She was more gutsy than your average cutesy girl.

        Then maybe I should let her tread in unfamiliar territory. I know...

      I should do that.

     “Wait here a second,” I said. “I’ll go get what we need.”

     “What we need? Are you planning on having us play chess? No fair!”

      “What a thing to be calling unfair…”

     How bad did you have to be at games where you used your brains to think that?
Fear not, Ruby, I won’t go that route. You won’t admit defeat if I did. It had to be something that seemed possible but wasn’t...

    Time to give her a glimpse of hell.

     I wonder, dear reader. Who did you expect to be the first victim of fanservice?

     Despite what she says. We aren't related by blood. I'm not even considered as a close friend with this family. Her uncle abandoned me. Her father despises me. And her sister, ch. I'm sure even she wouldn't mind crossing a line.

     But sure go ahead and keep calling me your big brother. That'll just keep the situation more....

    I left my room and went to Team RWBY's. Specifically their bathroom. It was just a quick grab at the four cups on the sink. Conveniently color coded for who's who's.

     Returning right away. Ruby was already messing around with DeusExMachina. She pressed a random button and it turned into a plunger. In shock she lost grip of the weapon and she left it on the ground, whistling ignorantly.

     "Oh, (Y/N)! You're back!" Ruby quickly brought attention to me. "Hm, what are you holding?... Is that my..."

      Indeed. I went and brought: Her red handled, fine thin-bristled, toothbrush. On the other hand, I had also stole team RWBY's shared toothpaste.

      "Y-you don't mean..." Ruby turned pale. Being uncharacteristically afraid. Maybe it's because she's been hanging out with that faunus girl. She seemed to be the type to have read stuff like this. Well since she knows what's happening I don't have to—

      "Are you going to stick that up my butt?!" Ruby exclaimed.

     ... Nevermind.

     "I-I had no idea you were capable of doing something so fiendish..." Ruby backed up and hissed.

     "I wasn't thinking of doing that at all!" I yelled. Hmph, as if I'd do something like that.

     "Really? I heard Yang would do it to a bunch of stalkers when she caught them. I knew the two of you were in leagues."

     "Don't lump me in with that blondie! Also that's gross, she didn't just beat them up like usual?!"

     “We’re getting off topic. If you’re not sticking it in my butt, then what the heck is that toothbrush for? What else would anyone do with a toothbrush?”

     That was some kind of question. If we took it out of context, she was the real pervert.

     “Ruby, you mean you didn’t know? A toothbrush is a tool that many people use to brush their teeth.”

      “A-Ah. That does ring a bell.”

      “Of course, if we’re being sticklers, it’s also used to clean other things. Great for getting at those hard-to-reach crevices around the sink or tub, etc. "

     "A toothbrush is a tool you use to brush your teeth, but what’s your point? You’re not going to make me brush my teeth, are you?”

     “Right. I’m not.” I nodded. “I’m not making you…because I’ll do the brushing.”

    “…?” Ruby cocked her head. The gravity of the situation still eluded her. “Um, I don’t get it… You’re gonna brush my teeth for me? Why? I mean, if you want to, I don’t mind…but how is that any sort of match?”

       She looked so dumbfounded.  Knowing that her aloof expression wouldn’t be on her face for much longer filled my heart with joy.

       “You  get your hair cut at a salon, don’t you? I get queasy about it. Having some stranger touch my head makes me weirdly tense.”

     “Well, I see what you mean. I wouldn’t want to get my hair cut by a stylist that I don’t know.”

     “Psychologically, people aren’t comfortable having their hair touched by anyone not close to them. I bet some girls would even rather be touched on their bodies than on their hair.”

     “Yeah…so?” asked Ruby, a touch of wariness in her voice. Unable to see where this was going, she was feeling anxious. Her vigilance was second to none.

     “It’s a matter of touch─a haircut is the simplest example, but I could give others. Would you ever trust a non-professional to perform a full-body massage on you? It’s that sort of thing.”

     “That sort of thing…”

     “Brushing one’s teeth is that sort of thing,” I said, though I didn’t know why I was speaking deliberately like I was giving a lecture. “You seem unperturbed, but having someone brush your teeth isn’t a common experience. Unlike a haircut or a massage, it’s something you can usually manage yourself and do take care of on your own.”

      Ruby gulped nervously. Slowly finally understanding where this was going.

      “Let me break it down, Ruby─getting your teeth brushed by another person is going to feel incredibly creepy. If you can keep yourself from freaking out for five minutes, you win. I’ll introduce you to my weapon dealer. But if you make a peep before the five minutes are up, I win, and I won’t introduce you to them.”

     Faced with the rules and conditions, the match that I laid out, Ruby laughed, like she was relieved. Actually, it was more of a snort, as if the wind had just been let out of her sails.

     “Wow,” she said, “the way you were making such a big deal of this, I was starting to get scared. Now I’m kind of disappointed.”

     “Are you?”

     “Yeah, bring it on. I don’t want to imagine having my teeth brushed by a total stranger, but you? I mean Yang would brush my teeth till 8, I can do this. Are you sure you won’t be the one to give in first, humiliated that you’re brushing a girl's teeth? I gotta say, there’s nothing you could do to me that I’d find embarrassing.”

     Well, lookee here. She thought she was dealing with an amateur.

     “Sure,” I consented, “if I break first you win.”

    “Yeah? I don’t know, it seems like a really easy challenge"

      “Let’s begin,” I said. “Sit there.”

       “You're going down.”

       Ruby plopped herself down on the bed willy-nilly, sending her skirt flipping up in a mess. I sat down next to her. I added a small amount of toothpaste to the brush, turned my body towards her direction, and placed my left hand behind her head.

     “Say ‘ahh.’'' I told her

      “Ahh.” She complied

       I had her open her mouth and inserted the toothbrush.

      "You've been eating too many cookies, lately." I whispered. "Let's make it so your teeth won't have to face the consequences of that."

       “Gh…mphh?!” Ruby finally seemed to grasp the danger she had stumbled into approximately a minute into the match.
Her expression shifted.

     I’d never seen a face look so alarmed... and ecstatic.

     “Mm…mmph, g-grk?!”

     Now she understood. The match was on.

      Yes. My talk of hair salons and massages had been misdirection. Getting your teeth brushed is on a different plane.

     We’re talking about fiddling around in your mouth. Not outside, but inside your body. Not the surface, but underneath.
Let’s not sugarcoat it. The truth is that it generates pleasure.

      In other words, it feels good.

      Brushing your teeth is such an everyday act that you become accustomed to it and don’t notice.
Yet it’s a stern fact.

       Caressing a delicate part of your body with fine bristles can only feel good. When it’s someone else doing it to boot, can anyone possibly keep it together?

       Ruby had guts. She didn’t bend to pain or humiliation.
     She was a masochist, you could say. A total, utter masochist.
    
     Which is exactly what made pleasing her, indulging her in this way such an effective means of breaking her spirit.
Tenacity felled by pleasure! Pride bowing to indolence!

     “Ng-gh…nmmphh!”

     As I focused on a spot behind her molars and scrubbed where tooth met gum, Ruby reacted in a most sensitive manner. Her body started to twitch and convulse.

     Her eyes seemed about to roll back.
This was getting scary in its own way…

     “Ng-gh…huph, huph, huph. N…gh, ahh, ahhh…”

     Unfortunately─I had miscalculated.
I’d failed to account for just how determined Ruby was. Not even pleasure could break this Rose.

     I thought she wouldn’t last two minutes, but she was gritting her teeth─well, she couldn’t since I was brushing them, instead her body went limp. But she withstood my strikes, my strokes, my pampering.

     This whole Niche fetish manga-like situation of being pleasured by her older brother must have felt really naughty to her, and yet… Hmph, not bad, Ruby. Not bad at all.

     She was inspiring me to try harder.
I began brushing her tongue. The underside of her tongue, to be precise, that part of the body was pretty much exposed muscle.

      “Ruby, you’ll feel so much better if you just gave up─correction! Give up and it won’t feel so good anymore!”

       She was in tickling hell. There was no way she could endure this.
Another minute was the most she could take!

      “Uh oh… Hold on?!”

     In fact, the one who couldn’t take another minute─was me.

      I’d focused on the psyche of the brushee and rushed into this without stopping to consider the very important matter of how I, the brusher, would feel.
It was a huge blunder. One I wouldn’t, couldn’t recover from.

      “Aaah… Pheuuu. H-Hnkk!”

       ……

       Holy shit!

       Her moaning gasps were making me feel all funny inside!

      My heart was thumping faster!

      Her every reaction was getting me worked up!

      What was this complex feeling, like we were breaking a taboo?! Knowing that I was pleasuring my own sister felt so immoral!

       Each audible scrape of the toothbrush, every frothing of paste in her mouth, began to feel less like cleaning Ruby's teeth and more like polishing my own soul.

      Was I satisfying myself the most by brushing someone else’s teeth rather than mine?!

      Was I so happy to be of use?!

      This was bad. Even the streak of drool spilling from the corner of Ruby's mouth, something I would usually just find gross, was instilling a strange sense of affection!

      If I didn’t stop working the brush immediately, something terrible might happen─but even though I knew that, knew that this was wrong, my hand seemed to have a mind of its own. Like some sort of automated machine (an electric toothbrush, even), it refused to stop.

     If anything, its movements grew more ferocious. The more I focused, the worse it got.

      Ruby's convulsions, likewise, intensified. She was clutching the bed sheet firmly in her hands, I guess because she couldn’t grit her teeth, but that still wasn’t enough to keep her body in check.

    And her face had turned like her namesake, like it was about to burst into flame.

      “Holy…” I said, without meaning to. I managed to swallow the words just in time—but the ones that almost escaped my mouth surprised even myself.

      Holy. She looked so cute.

     I've despised this family. But I knew it was unreasonable to hold that hate with the people like her. That was just grouped in with them by blood. Despite her being a bit annoying. At most, I tolerated her.

      But I never found her so cute before.

       This was insane.

      Was Ruby always this cute?

     This was an illusion, all an illusion! I was just drunk on the bizarre situation! I saw that, knew it was true!

     A-And yet…

     “N-Nuhhh…” I moaned as if joining her in chorus.

     There was some kind of synergy. I lost sight of myself. My mental circuitry even entertained the possibility that I’d been born into this world just to brush Ruby's teeth. What an idiotic mental circuitry mine was.

       How could brushing someone’s teeth backfire so horrendously? I had stumbled into dealing with dark, forbidden arts.
But it was far too late for regret.
Ignorance was no defense. Ignorance would be my undoing.

     This was beyond my control. My only choice was to let the pieces fall where they may.

       “R-Ruby…”

     It’s terribly attractive.

     It’s terribly enticing.

     It’s terribly numbing.

     By the time you realize…

    By the time I realized—I’d pushed Ruby down onto my bed.

     With my left hand still cradling her head, I’d leaned over her and pinned her down.

     She was smaller than me, she went down smoothly, not resisting.

     I looked at Ruby. Gazed at her.

      She was swooning, melting into puddles.

      She was in heaven.

      “Ruby. Ruby. Ruby…”

      I repeated her name, over and over. Every time I spoke it, a fever flared up from deep inside me.

      Ruby's body, too, was hot.

     “(Yw/N) ~…”

     Thanks to the toothbrush inserted in her mouth—well, probably even if it hadn’t been there—she was lisping, her pupils unfocused..

       Yet she said—bravely, she said: “(Y-Y/N)… Go ahead.”

     'Ahead' ?!

     Ahead to where?!

     That’s how I’d wisecrack under normal circumstances, but I was feeling all sloppy as well.

      Sloppy. Slippery.

      Syrupy. Seeping.

      Woolly. Woozy.

      Wobbly. Worming.

      I gently removed my left hand from behind her head and slowly extended it toward her breasts—

     “What in tarnation?”

    That was when a boorish, insensitive, deflating—no, a saving voice cut in.

     When I turned to look at the door. I see the rest of team (Y/N) standing by, looking rather speechless at the sight.

      •••••

      Nothing happened between us after that. Rather, it was hard to even think of doing anything. Suprisingly, the rest of the team didn't talk about it any longer. Saying stuff like this is to be expected eventually.

       "... But I still have no idea what came over me today." I hid my face with my hands in shame.

      Nite looked at me from the corner of his eyes. A smirk on his face before staring off to the ceiling.

      "Sorry, I finished watching Monogatari recently and... "