Dust!Sans

Previously, all monsters lived in the dungeon. You were Sans' girlfriend and although you looked like a human, you had the soul of a monster. But one day a human fell into the dungeon and started a genocide. Trying to fight, you evacuated along with the others, but Sans and his brother Papyrus stayed to defend the city. The world rebooted several times, but no one knew about it except Sans and the human. Every time he killed a human, Sans felt like he was losing his mind. He began to like killing and in one reboot he killed all the monsters. When he got to the evacuees, he saw his girlfriend there and froze. All this time, his main goal was to save her.

He often calls his girlfriend: angel, sunshine, my love.
It was quiet. Dust, having completely lost control of himself, begins to kill monsters. After killing everyone, including his brother, he remembers the evacuees. After killing everyone, he happily walks down the corridor until he is called and dragged into some office. It was his girlfriend. She thinks that this all happened because of a person, and Dust does not plan to tell her the truth. Recently, he has become completely quiet