For the Love of Science (Book 3 The Ultimate Crossover)

Flowey and Chara

I went back to school on Monday. That surprised Alphys and Frisk who both asked if I was ok to be there, I'd just lost grandma after all. "I'm ok.. It hurts, but loss is apart of life.. She'd want me to continue my studies. So will you guys catch me up on what I missed?"
"O-f c-cour-se!" Alphys replied immediately. "Yeah! I missed having you around to help me!" Frisk agreed. I chuckled. "Great. Thanks." I offered them a small smile. "I miss helping you too."
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After school I went with Frisk to help them with their homework, much like old times. Toriel and Asgore were happy to see me, wishing me condolences again. I'd waved them off, telling them the same thing I told Frisk and Alphys. I went back to the Underground by myself after. I sighed as I looked at the charred remains of Sans and Papyrus' house. They'd sacrificed so much for WD. Sans sacrificed so much for WD. I sighed. I had to make it up to them. I set to work immediately, collecting and getting rid of the burnt wood. I got some fresh wood to cover up the basement.
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I started to look for a new place to build the machine. In my search I was met with a lush, beautiful, place. The waters glowed a pristine blue and flowers of the same color swayed, echoing the dreams of monsters who wished to go on the surface. I was glad those dreams came true. I ended up getting lost in the expanse of beauty. The crystals shown brightly, almost like real stars. I could help thinking that this would be a romantic spot for WD and I to go on a date.. I blushed at the thought. WD and I.. Quite the thought, but it could probably wouldn't happen even if I did save him. I didn't even know if he loved me back.. I shook myself out of my thoughts. I spotted a door not far away from me.. A grey door. "Hm?" I walked towards it. "A potential building spot..?" I wondered as I grabbed the handle and twisted, pulling it open. My eyes widened in shock at what- no who- I saw. He stood stock still, 7 foot tall and straight and proud. His back was facing towards me, but I could recognize him anywhere. My crush, WD Gaster.
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"I must be dreaming.." His head twitched in my direction. "Mari?" I blinked. "WD.. How..? How is this possible?!" He fully turned to me. "There are occasions when the void clashes with the time/space. I cannot leave this space.. This grey room, but those in space/time can interact with it. Hence our interaction now." I nodded slowly. "Have you interacted with others before?" I asked. "A couple of times.. With a child named Frisk." I perked. "Frisk?! They're my friend." I commented. "Are you? That is good. I must warn you though.. Be careful around them.. They are not what they seem." I was confused, but I nodded. "I'll take your word, WD." He nodded. "Great. While you're here though, Mari.." He slowly walked over to me. I looked at him in slight confusion. "WD?" He stopped next to me, placing a hand on my face. I erupted into a blush. "W-WD.."
"I don't know when I'll be able to do this again, outside your dreams."
"Do what? WD what are you pla-" He cut you off as he pressed his teeth to my lips. It was heaven. He pulled away. "Thank you, for giving me the chance, Marionette. I love you.."
"I-I love you too.. My stars I didn't think you felt the same way!"
"I've felt this way for quite a while.. You must go soon.. The void will be splitting away from space/time soon.."
"I see.. WD. I need a new place to build the machine!"
"Use my lab. It's in Hotland."
"Wheres-" I was thrown out suddenly, the door slamming and disappearing before my eyes.
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I tried finding Hotland, but I knew nothing about the Underground. This had been a bad idea.. "Howdy!" A voice said behind me, making me jump. "I'm Flowey, Flowey the flower. Boy you look so lost!" I turned to said flower. "I am. Do you know the way to Hotland?" Flowey blinked. "What are you? You don't look human." He said with a hint of uncertainty. "No matter I guess! You ARE friends with that S M I L E Y T R A S H B A G after all." I was on guard immediately. Wait. He knew I'd been with Sans. He was small, hard to notice.. I narrowed my eyes. "Saboteur!" I snapped. Another voice came from behind me. "Sorry partner.. But we can't have the likes of that nosy scientist ruining our little game. I woulda reset by now, but someone has more determination than Frisk." I whipped around to see Frisk.. But not Frisk. They wore Frisk's clothes, their physic, even their face, but their eyes were red. Determination red. Flowey took this second of distraction to attack and ensnare me with vines. "I'll be taking your soul now." The Frisk look alike said as they approached. 'No!' I wasn't giving up that easy. I made an ink portal below me and lashed my tail through Flowey's vines, dropping inside much to their surprise. Seems they didn't know about toons or animatronics. Good. I could use that to my advantage. I appeared inside Sans and Papyrus' house on the surface, startling Sans. "what the heck mari!"
"Sorry Sans. I found our Saboteurs." He sat up straighter. "who?"
"A monster named Flowey and some Frisk look alike." Sans' eyes blacked out. "chara.."
"That their name? Either way they said WD was a hazard to their plans and they needed my soul for something called reset."
"you? oh! so that's why.."
"Care to explain what's going on and why I'm involved?"