(I didn't have an Underfell version of this picture, but I thought it would fit perfectly)

Sans soon fell asleep in Papyrus' arms and cuddled closely against him. He began audibly mumbling in his sleep, "B-Boss.... I... N-need.... You..... I.... Want....y-you..." Hearing this, Papyrus, known to blush rarely, became brightly red. He knew that Sans loved him, he just was surprised to hear him say it. Suddenly, a monster and their gang stopped Papyrus in his path. Despite being the most feared, Papyrus occasionally had a challenger; he scoffed at the monster's "courage" . The monster chuckled, "So you're the big bad 'wolf' now, aren'chya 'Papy'" A shaky chuckle arose from the controlled gang, and Papyrus cocked an eyebrow. Only HIS brother was allowed to call him Papy. He decided to remain calm as in to keep Sans from waking and freak out.

"If I were you... I'd rather you back off before you wake my possession. If you do, you'll have a very VERY bad time... And I mean a BAD time..." As he said that, his red magic flared around his eye. The monsters shuffled uneasily, but remained in the way. One such was planning a surprise attack. The gang held their ground as Papyrus prepared to summon a torrent of bones, each laced with cartilage shards and splinters. "I said, back OFF!!!" He hollered before being hit unconscious. He fell to the floor, dropping Sans and blacking out.

Sans' Pov

Sans landed on the fluffy snow and gasped from the sudden awakening. He rubbed his skull before being pinned to the floor aggressively. "Alright boys, let's teach theses two no-gooders who the REAL bosses of the Underground are. Hehehe" they all began getting dressed as they ripped Sans' clothes off of his frail body. One of the many gang member decided to tie Papyrus' body to the tree, facing the scene so he could watch Sans' misery.

After a few hours of waiting, and their patients growing thin, Papyrus finally awoke to Sans getting pinned and raped. All either of them could do was scream, curse and cry. The sight nearly ticked Papyrus beyond imagination, as his only love and brother was used and beaten. Sans, after a rough amount of unconsented sex, laid in the snow, his eyes half open as his body was being finished with. He was completely worthless, he felt, and decided he no longer deserved his brother's love and affections. The gang, after taking their turns, decided Papyrus didn't have enough to see, and so decided to start battering Sans nearly to dust.

Papyrus could only feel rage at this point, he didn't care if anyone was in his way: He was going to avenge Sans' virginity. The thing he was going to ask to take. His magic began prying the binding apart, and lashed at the monster, dusting each and everyone of them within seconds. He ran to Sans, tears pouring, and held his broken brother. Sans' soul was cracked...