This one's already pre-written, so I thought I'd just post it here and be on my way. Anyway, enjoy?

*Meanwhile...*

While Patchouli was with Remilia at the dining table, Marisa was busy nabbing all sorts of books that interested her. She was flying around collecting books when she noticed something out of place. She found that one of the selves was bluish in color next to a blue-colored wall as opposed to the wood brown that the wooden walls are supposed to have. Curious, she went to investigate it.

"Strange. This one's blue? Heh, that means something's gotta be hidden here." said Marisa to herself as she examined the bookshelf. She tried the first thing she knew and that is to fiddle with the books to see which one is the activation switch, and sure enough, a book that's thicker than the rest of them was the one. As she pulled the book out, the bookshelf vibrated and slowly slid itself to the right, revealing a hidden passageway behind it. "Jackpot~!" Without further ado, she threw the book elsewhere and took the book-filled burlap sack before dragging it along as she went inside the passageway, not knowing of the dangers that may lurk inside, not that she ever cared, but this carelessness may or may not be her demise as we would soon see.

As Marisa walked along the passageway, the surrounding walls slowly start to change colors from blue to a light green. Eventually, after a minute or so walking, she encountered a stone door that seemed to have some magical runes inscribed onto them.

"Placing runes so I can't break in, eh? Patchy, you silly bookworm." Marisa walked to the door and took out a device from her pocket which she would then place on the door before standing back. The device glowed and within a matter of seconds, the runes all started to disappear one by one. "Heh. Too easy!" With a push, she easily opened the door and walked right in along with her nabbed possessions. Unbeknownst to her though, there was a hidden tome above the door that would reapply the runes should they be disabled.

*Meanwhile...*

Patchouli and Koakuma had just entered the library to find the mess that Marisa had left during her raid. The library was in shambles once more, books scattered, bookshelves missing their books with some overturned, and even the candles put out. Furious and worried, Patchouli stormed towards the big table she always sits and picked up a magical tome. "Koa, we need to find Marisa quick! We can't let her find that place no matter what!" she said as she cast a spell to summon clones of her devil assistant. "Now all of you, clean this place up!" she ordered the clones whom all nodded and started working to get the library cleaned up.

"Um, Master? I don't think we should waste energy trying to find her..." Koakuma said in a sheepish voice.

"Huh? What's that supposed to mean?" Patchouli asked back, confused.

"Just look..." Koakuma pointed to a part of the wall in the adjacent side of where they are, the blue-colored wooden walls, with the secret door opened.

"Damn you, Marisa..." Patchouli cursed under her breath as she quickly made her way there followed by Koakuma.

Now back to Marisa, she was just aimlessly wandering down the single hallway and was just starting to get bored until she stepped on something. Before she could realize, her feet were wet and it started to feel slightly slippery. It was then she realized that there's water in front of her.

"A flooded hallway, huh? Or is it just another way to drive me away, I wonder?" Marisa said with a grin as she placed her burlap sack where the water won't reach and started to take off her dress and hat and placed them right next to it, leaving her only in her lingerie and bloomers. But just as she was about to go to the water, she thought she heard the sound of walls closing, but she paid it no mind and continued back to what she was about to do. "I can't wait to see what lies underneath this place! This must be where she keeps the dangerous stuff!" she said as she began her stretches. After doing some stretches and breathing exercises, she began walking into the water with only her broom and mini-hakkero in hand. "Alright! Here I come, treasure!" After she had walked until she's chest deep, she leaped into the water and dived down, barely missing the sunken stairs hidden under the water. Close, she thought, as she then navigated her way in the water, using her mini-hakkero as a light source.

Deep in the flooded hallway, she gracefully swam in the water as she kept on the lookout for any loots she could steal. So far, for the one minute she has been swimming, she only found nothing but gems and jewels that she could only identify as ordinary gems meant for decorations. 'Just where does this lead to? This better be worth the exploration.' Marisa thought while looking for any more loots to take.

Another minute has passed, and she could feel her chest tightening from the lack of oxygen in her chest. Her chest would make small heaves for now, but she's now worrying about her air more than anything. After what seemed like an eternity, she finally emerged out of the same flooded hallway she has been swimming in circles in into a large open area. It was a very large cubic room that were decorated with some ancient-looking mystical stones instead of the rocky cave walls she was previously in. Marisa gasped in awe as she marveled in on the sight before her. It was only when her chest gave a large heave that she was reminded of her suffocating lungs. Looking around in panic, she finally found an air pocket high above her and started to make her way there.

'Dammit! Why is the surface so far away?' she thought as she swam with all her might, her body starting to feel heavy and weak from the lessening of air and the increasing amounts of carbon dioxide building up inside her lungs. Just then her chest gave off a massive heave, taking her by surprise and making her cough out a lot of air, stopping her in her tracks. After getting taken by surprise by her chest heaving, she quickly resumed her way up for the surface that seemed so far away from her. She felt lightheaded and sleepy, but the ever growing pain in her chest was keeping her awake, yet at the same time, she could feel her lower regions starting to quiver and her legs starting to shake under the feeling of pain and pleasure at the same time. 'No, no, this isn't the time for this! Need to get... air...!' These thoughts were running in her head the entire ascent. She was starting to feel weaker and her movements slowing. She was getting so close to the surface too, she can't just give up now, yet her body was getting weaker by the second. Just then, the thing she thought she wouldn't get to in time finally reached her - LIFE-GIVING AIR! Oh, how deeply she must've inhaled when she broke the surface. Coughing water out of her system, she weakly started to gasp for air while keeping herself afloat with her broom. "Finally... *pant* ...Air... At last..."

Patchouli was getting ready to go into the room along with her assistant Koakuma. They're both dressed in wetsuits and geared themselves with full scuba gear, a harpoon, and some capsule bombs.

"Let's go catch some fish, Koa, and let's catch ourselves a witch while we're at it!" Patchouli said as she put on her gear.

"Right back at you!" Koakuma said with a nod.

And with that, they both ran into the secret hallway as fast as they could.

Back at Marisa, she was lazily floating on the surface to catch her breath when she suddenly felt a tug on her leg. She managed to get a quick breath before she was pulled under. She looked down to see some rope had somehow wrapped itself around her leg, and not just any rope too; it was an anchor tied to a rope, and down below she could see a shadowy figure pulling on said anchor. She tried to uncoil the rope, but due to the force the rope was pulled on, it wrapped very tightly around her rope and she could not get it off no matter what. Thinking it might be a trap, she decided to blast the rope with some danmaku and then swim up for some air. She managed to do so, and this time a hook went soaring towards her, luckily it barely missed her, and she managed to get away.

"Fwah! What the hell is that!?" Marisa said upon breaking the surface. "Something's gotta be down there protecting it all!"

Before she could swim away though, she could feel another tug on her leg. Now prepared for what's about to come, she took a deep breath just before she was pulled under again. Thinking she may only see the harpooned hooks, she instead found herself face to face with a creature that is out of this world. The creature was humanoid, but it was also part fish; particularly, the creature was a bipedal fish that, from the looks of it, could stand up like humans can, and it's blue in color. Whatever the creature was, it looked rather angry as it passed a death glare towards Marisa. Before Marisa could even register what she was seeing, she was brought down towards the bottom of the flooded room and within seconds she could feel the floor ramming hard against her back, making her lose some air as she screamed in pain. The fish creature, seeing that Marisa was at a disadvantage, grabbed Marisa by the leg and slammed her onto the floor again before releasing her and began to prepare a kick. Marisa was able to dodge the incoming kick and swam a distance away as she fired a barrage of danmaku towards it. Her danmaku didn't seem to do anything however as the danmaku just brushed off of its scaly hide as if it was nothing and could even hold a danmaku bullet before throwing it back at Marisa at high speed, hitting her square in the chest, making her lose more air as the reflected bullet was enhanced and it actually burned through her bra and into her chest, leaving a burn mark there and it died before it could penetrate her chest.

'What the hell is this thing? Why is this being kept here? Is this what Patchy uses to guard her secrets nowadays?' Marisa thought as she tried to assess her situation. She's currently at a major disadvantage with most of her air already depleted and nothing she did affected it at all. Just what chance does she have? Would she even get out of here in time? And how did it reflect her danmaku? All these thoughts were racing in her head as she tried to come up with a plan of escape. Just then her chest gave out a massive heave, sending her in a frenzy as the sudden shock pushed more air out and sent massive jolts of pain throughout her body. She was now reminded just how low her air was, but with the fish creature still keeping her down, there's no way she could get out, but she just have to try...

Patchouli and Koakuma were running down the hallways to locate Marisa's location. It wasn't long before they found what they were looking for.

"These are..."

Koakuma held the clothes that were strewn about near the flooded hallway. They both recognized the clothes very well.

"Yep. That's Marisa's clothes." Patchouli said to confirm Koakuma's question. "So she did go inside..."

Just then they could see a flashes of light coming from the water along the flooded hallways. They knew Marisa was down there and seeing as she's unequipped with anything, she doesn't have much time left.

"Come on, Koa! We got no time to waste!" Patchouli said as she jumped into the water while putting her regulator on.

"Right behind you, Master!" Koakuma said as she followed suit.

Aiming her mini-hakkero at the Merking, Marisa started to fire some danmaku at it, but, being in its home turf, it was able to dodge every single danmaku bullet and swiftly made its way to Marisa and delivered a punch to her stomach, forcing more air out. Marisa flinched and tried to hold her air in by clamping her mouth shut, but the fish was smart enough to deliver another punch to her stomach to force her mouth open. It only took three more punches before Marisa would scream out her air in pain due to all the punching. Just then she started to hyperventilate and curl up in pain as more air left her, her lungs already almost empty. She had been under for close to 4 minutes and it's clear that she has lost the battle from the beginning, so as an act of desperation, she aimed her mini-hakkero at the fish humanoid and fired a flash, blinding it temporarily as she made an attempt to swim for the surface. It seemed to work for a while, but as she has little to no air in her lungs, she has lost most of her buoyancy, thus unable to ascent as fast as she would've wanted.

'Air... Air...!' It was all Marisa could think of as she felt her body getting heavier, the pain in her chest increasing tenfold, her lungs burning like wildfire, her limbs aching worse and worse, and her vision starting to dim. Her legs then started to twist as she received cramps on both legs. She screamed out more air in response, but she still tried to persevere and went on swimming even though she noticed that she's starting to sink as she swim. Then, as if adding insult to injury, she could feel her legs being wrapped in chains before getting pulled under again, hitting the floor hard which caused her to expel all of her remaining air in one scream. She could see the fish approaching her and tried to move but her body then started convulsing and hyperventilating as she began to draw water into her lungs while they tried to reject them to no avail. She thrashed about and screamed in pain at her mightiest though the only things that came out of her mouth were muffled gurgles and choking sounds.

'No... this can't be... I can't... end like this...' Marisa thought as she lay on the floor of the flooded labyrinth convulsing and choking on the water that only worsened the burning in her lungs as opposed to treating it. She could feel her body losing its functions, one by one her limbs fell and become heavy like lead, her vision dimming, and her throat constricting to not let water in, choking herself. She then could feel the fish stepping on her crotch area and seemed to have the look of a maniac on its face.

'Go ahead, fish... I'm all yours...' It was all she thought before she started to feel sleepy and slowly lost consciousness. The last thing she saw before she lost consciousness was a bright light enveloping the fish creature followed by dust...

For this one, I have a few endings in mind, but I don't know which one to choose. The endings so far I have are...

* Good End
* Bad End
* Happy End
* Weird End
* Unexpected End

Just comment on which one do you want to see first.