Underfell Sans is a dirty sinner, he likes reading yuri and lemons with no regrets, loves/hates his brother UF Papyrus, He can't stand US Sans and the way he fan boy's over him While UnderSwap Sans or Blueberry is an innocent childish skeleton, who likes sweet things, romantic fanfictions, secretly likes yaoi and yuri, loves his brother US Papyrus and has been trying for 2 years to be Underfell Sans's friend