The entire idea of this fic is based on Amakusa's interlude. Minor spoiler for said interlude: after temporarily betraying his Master in an attempt to get his hands on a grail, being beaten and then subsequently forgiven, Amakusa insists on receiving punishment. The Master then asks him to clean their room, which he promises to do with gusto.

There will be some Amakusa/Gudako, though it'll be rather minor before it develops into any actual romance. Also, since it's Gudako there'll also be plenty of mention of other pairings involving her.

And for the record, the title and Amakusa's quote in the description are from a translation of the Japanese interlude and not the NA version, since I just liked the sound of those better.

Shirou Amakusa Tokisada – one of Chaldea's rare Ruler-class Servants – was walking through the hallways of Chaldea, carrying a bucket with soap water and a mop in each hand, a dust rag slung over his shoulder.

If anyone had seen him like that, they would've certainly raised an eyebrow at this odd behavior for a Servant… if they saw him, that is.
Amakusa had been taking special care to start gathering these supplies right before the next rayshift, when all of Chaldea was preparing and the movements of a Servant not in the current team weren't being checked. Not to mention that the supply closet was unlocked because someone had to grab some cooling fluid for one of the machines, meaning he didn't even have to borrow the key to it, either. Well, with his Noble Phantasm he could easily use Magecraft to unlock it, but acting so secretively in the base of his Master would have left a bad taste in his mouth, so he preferred to avoid doing that.
(Amakusa decided not to acknowledge the irony of that thought, considering he'd quite literally attempted to betray that exact same Master not a week before, which was how ended up doing this in the first place.)

Though it wasn't like Amakusa was doing anything wrong: this was following a direct order from said Master, after all. And he wasn't embarrassed over having to clean either. Rather than any humans' reaction, this secrecy was out of concern for how some of the Servants would react. In particular a certain Japanese Berserker with a history of 'disliking' those too… 'close' to her Master. And while this order wasn't given out of any particular closeness or affection towards the Ruler, Amakusa could imagine Kiyohime not reacting well to him receiving special attention, even if it was only to clean.
Thinking it over, that it was a household chore might bother her more because she wanted to do all the housework herself. Something about wanting to prove she was the perfect wife for her 'husband'… Well, due to their Master's easy-to-like personality Kiyohime wasn't the only Servant who'd consider such behavior an issue, but Amakusa rather not dwell on just how dangerous this seemingly simple chore would actually be if anyone found out.

And so it was that he ended up delaying the punishment he'd asked for after the fiasco of him trying to obtain the corrupted grail until now, when there would be a minimum amount of people and Servants roaming the halls.

Having been in Chaldea for a while now, Amakusa easily found his way through the many hallways – despite the added difficulty of the rather roundabout route he was following – and reached his Master's room. He'd informed Gudako that he'd be cleaning it today, so she said she'd leave it unlocked (not that she needed to fear humans stealing something from a person who commanded the loyalty of so many Servants and said Servants wouldn't be stopped by an ordinary lock either, but it was the thought that mattered). And indeed, when the young(?) Ruler approached, the doors slid open automatically.

He stepped into the room – and immediately concluded he would easily be done before the Rayshift team returns. It was a minor Singularity this time that wouldn't take a day, but all he had to do was dust and arrange some things, make the bed, take out the small trash bin that was half-filled and perhaps mop the floor. Except for some disorganization on the desk it seemed like his Master was not that messy a person, and Amakusa suspected that if everyone actually had the time to clean their own rooms between all this saving the world they were doing, this room wouldn't even need anything beyond perhaps some mopping.
Well, he had heard that until shortly before his arrival the other Servant that always looked up when the name 'Shirou' was spoken used to clean rooms, but due to the increase in Servants he'd been too busy with his job in Chaldea's cafeteria to do so anymore. In particular since a new batch of Artorias arrived. Goodness, King Arthur (all of them, even the younger version) could eat.

Amakusa placed the bucket and mop on the ground for now, deciding to keep the mopping for last. First, he started with arranging the stuff on the desk while simultaneously dusting it, carefully checking before he threw anything trash-looking into the waste bin. Without Gudako having mentioned what could and couldn't be thrown away beforehand, he decided to only trash some loose wrappings from the occasional caramel and snack, and an empty bottle of some soft drink. The amount wasn't so much that he suspected his Master to risk health issues, though he did note she must have a bit of a sweet tooth.
While cleaning the desk he also took care to neatly place any loose pens in the pen holder and made a neat pile of the loose books and papers strewn about. He didn't want to open any drawers without his Master's permission, so that was about all he could do there.

Done with cleaning the desk, he moved onto the next target: the bed. Gudako did have a nightstand, but all that was on it were a lamp and book. There was no dust present, so he just ignored that in favor of making the bed. He took the liberty of gathering a clean bedsheet, cover and pillow case from the laundry room earlier. Smoothly exchanging them with the used ones, he placed the old laundry in the basket with crumpled-up clothes he'd only just noticed standing in the corner. Another basket he'd have to empty later on, he made a note to himself.
He lied on his stomach to check under the bed to ensure there was nothing that fell underneath it, and apart from some dust bunnies he didn't see anything. He'd have liked to clean those up as well, but unfortunately the vacuum cleaner – such a useful invention – was out of commission due to lacking bags, and since cleaning wasn't that high on Chaldea's current priority list no one has tried to acquire any from one of the more modern Singularities. Perhaps King Gilgamesh might have some in his Gate of Babylon (honestly the more random junk the various Gilgameshes pulled out of that, the less it seemed like a treasury), but child Gil couldn't remember if he had any, Caster Gilgamesh had felt insulted by the request, and not even Gudako had dared to ask the adult Archer Gilgamesh.
Amakusa decides to just consider himself lucky that the rest of the room's floor was clean enough that he could still mop it and left it at that. In hindsight, maybe he should've brought a broom instead of the vacuum…

He was just about to push himself up when a piece of paper stuck on the underside of the bed caught his eye. He hadn't noticed it before because it was so neatly stuck to it – definitely done on purpose – but since he couldn't imagine Gudako sticking something there he pried it off to hold it into the light for a closer look.
Now able to see it properly, he could tell it was a talisman. In his friendship with Fuuma Kotarou the ninja had taught him about the various kinds of talismans, and so Amakusa recognized it as a talisman for sharing information. Particularly, if one was holding the partner talisman and focused on it, they could perceive what was going on through it. Basically, a tool for spying.
Amakusa could've believed that it was merely to ensure the Master's safety if it had been placed on a wall or something, but considering it stuck to such a hard-to-find location he could only conclude that spying was exactly its owner's intention. If someone wanted to spy on Chaldea's interests this would've been placed in the control room, so this would only have been placed by someone with a personal interest. And among the Servants – because really, only a Servant would use an actual talisman – there were plenty with interest in their Master. Other than this Amakusa could only conclude that it was not the work of someone used to handling talismans – like for example Kotarou – since the writing was a bit too sloppy, as if the person was trying to write while looking at an example.
He decided that for the moment, placing the talisman on the desk for Gudako to find with a note explaining what he knew about it would have to do, and Amakusa moved on to his next task.

Soon enough any remaining dusting and then the mopping was done, and Amakusa took a moment to appreciate his work. He hoped his Master would enjoy his effort, though he still felt this was rather minor punishment. Well, she initially didn't intend to give him any punishment at all, so he doubted she'd agree to giving more.

Everything was in order and he should leave… but even for someone like Amakusa, there was one particular curiosity in the room that he couldn't help but wonder about.
Namely, a certain drawer. A locked drawer. A locked drawer, but the lock was so enormous that one could club another person out with it. Unlike one usually does for precious belongings, Gudako wasn't even trying to hide that she wanted to keep people out of this particular drawer. It was purely protection oriented, disregarding any aesthetics and convenience, and considering the slight amount of prana Amakusa could sense in it, it had several layers of enchantments, too. He suspected that even a Servant would have trouble getting past that if they lacked the proper skills to deal with these kinds of wards.
… Did Gudako perhaps get one of the Caster servants to do this? No, enchantments like these must've been the results of cooperation. Honestly, this level would be good enough to secure some of Chaldea's sensitive, absolutely-no-rampaging-servants-allowed-near-them systems, and she instead stuck it onto a lock on a drawer. The entire room would give before the lock did!
The Ruler was not one for sticking his nose into others' private business, but he had to admit that he'd be asking Master about what could be in this fortified drawer next time he caught her alone (because he had no intention of signing his own death warrant by publicly admitting he was alone in Master's room: some Servants really were that possessive).

Still, other than this lasting mystery he was content with his work for the day and gathered the cleaning tools before heading out. The storage room was still unlocked by the time he dropped everything off there, and so he walked away with none the wiser.

On his way back to his own humble room, he ran into Mash.

"Oh, Mister Amakusa! Hello," The Demi-Servant politely greeted him with a small bow, which he returned. Honestly, he'd prefer she treated him as casually as Gudako did, but considered outright asking it of her a bit much.

"Good day, Miss Kyrielight. Since you were with Gudako, I assume the Singularity's already been dealt with?"

"Yes! We cleared it without much resistance, and I think Senpai's already returning to her room. Did you perhaps want to speak with her?"

"No, I was just curious. I'm glad to hear it went well."

"I see…" Instead of excusing herself like expected, Mash remained standing in front of Amakusa, looking at his face. But rather than his eyes, her gaze seemed focused on something else.

"Miss Kyrielight? Is there something on my face?"

"Oh, no! There's nothing wrong. I was just wondering if something good has happened to you."

"Hm… nothing recent that I can recall. Why do you ask?"

"I just saw that relaxed smile on your face and assumed there was a reason. My apologies for making assumptions."

"No, it's fine. Now that I think of it, I did just handle a particular task quite well, so perhaps I'm simply content with that."

"I understand, that must be it. Well then, if you'll excuse me…" With another polite bow Mash left him, presumably retiring to her room herself.

As Amakusa regarded the girl's back disappearing around a corner, he moved his hand upward to his mouth. Certainly, when he relaxed his facial muscles, the corners of his mouth did seem to rise a little without him meaning to. But despite what he'd said to Mash, he doubted cleaning Master's room was the cause. Though when he thought about it, maybe it was after all? Thinking back on it he did find the peaceful work of tidying everything up quite relaxing compared to the hectic life of combat he'd grown used to as a Servant.
All in all, he actually found the experience quite enjoyable.

… Maybe he should ask Master if he could go clean her room on a regular basis?