"what's wrong, buddy? you look like you've seen a ghost."
– Sans asks Chara why they look so uneasy.
Sans and the rest of Frisk's friends meet Chara after the latter has scared off Flowey. Sans wonders why they are acting so strange. Chara attempts to kill the group, but Sans attacks them with psychokinesis, asking them where they got so much LV. Realizing that Chara is the one that he had been having nightmares about, he attempts to kill Chara to protect his friends while trying to explain to them about the nightmares. But he is stopped by Toriel and Papyrus. When Chara tries to stab Toriel with their knife, Sans uses his psychokinesis again to immobilize them. Toriel, angered by Sans' attempt to hurt "Frisk", sends Fire Magic at him. Unable to dodge the attack since Papyrus was restraining him, Sans was hit by the Fire Magic and died in his brother's arms.
Sans' appearance is identical to how he appeared in Undertale.
His personality is very much the same as in Undertale, Sans cares about his friends and would do anything to keep them out of harm's way, despite the consequences of doing so.
Despite the fact that he annoys Papyrus a lot, Sans cares very deeply about his brother.
Frisk and Sans Are Very close, since they Are Best friends, While Frisk and Chara Switched, At first. He thought Chara is Frisk.
Sans and Toriel are very good friends, but Toriel would not allow him to do anything to hurt Frisk. She even went as far as attack him to protect "Frisk", not realizing Sans had only 1 HP and was horrified when her Fire Magic killed him.