Disgaea and undertale crossover thing

Where is this??

Frisk was confused. It was quite understandable, I mean any other child who falls down a cliff and finds two signs pointing opposite directions would be confused. Frisk looked at both signs back and forth and decided to go to the sign that said "The Netherworld". Frisk was met by an empty land that looked like a desert. They were even more confused. "Where-"
"Look plip! There's a child, we should help them plip!"
Frisk looked over to see a group of... Unique individuals to say the least. They all walked over to her, they were led by a man with dark blue hair and yellow eyes. "Hey are you lost?" He said softly while bending his knees to reach their height. "I think" Frisk replied, causing a pink haired woman to gasp dramatically. "Poor thing! I say escort them to safety Sir Killia!"
"Wait Seraphina.."
All eyes turned to a male with shoulder length green hair. "According to my Clairvoyance, I don't think this child belongs here."
"What in the super hell do you mean Lil C'sto?!" Shouted a muscled red haired man
Frisk tensed at the sudden shouting. "Look what you did you monkey! You scared the poor kid!" Seraphina yelled at the red haired man. " Sis Seraphina screaming at him will scare them more" retorted a short silver haired man, if he could be called that. "Killia, everyone's going crazy, what do we do plip?" A small yellow haired girl asked, she was almost the same height as Frisk but shorter, Frisk recognized that voice before, that was probably the same girl who found them. "Everyone be quiet! You're scaring the child!" Killia said, raising his voice slightly to get everyone's attention but also trying not to frighten Frisk anymore. "Don't be scared kid, we won't hurt you. Anyway, what is your name?"
"Frisk"
"Is there anyplace you should be right now?"
"I'm not sure I just-"
"Stop right there!"
Everyone looked to see a skeleton wearing the most stupidest costume ever, and next to him walked a smaller skeleton with lazy eyes and slippers. "Christo, I now see what you mean by the child not belonging here, I believe they're here for you" Killia said, first addressing the green haired male and than Frisk.
"Of course we're here for the human! Hand them over or I, the great Papyrus, will force you to hand over the human!"
"We apologize for the inconvenience, Papyrus, was it? Please take the child" Christo said calmly
"Alright no resistance that's cool. C'mon kid, time to go" the short skeleton said while gesturing his head behind him. Frisk had no idea what to do so they went with the flow and walked over to the short skeleton. "Um bye now" Frisk said to the group of people and they waved bye at the kid that they met out of nowhere. "Hey Papyrus will I see them again?" Frisk asked as they walked towards the other sign labeled "The Underworld"
"I'm not sure, will they Sans?"
"I dunno, only if you want to kid"
Frisk nodded and they went to the Underworld.