DOUBLE-CLICK THE FLAG (READ) Use arrow keys (Up, Down, Left, Right) to move, use key Z to select, and use key X to deselect or go back. If there is blue bone, then don't move, if there is orange bone, then move. You can go into the items section to heal. Try to time your attack correctly after pressing the fight button. You can spare him in the Mercy button after 20 attacks, see what happens ;)
↑↑ READ THE INSTRUCTIONS CAREFULLY AT TOP ↑↑ Credits to Undertale, the original game this is based on. Sans battle made by Parindraa