Xbooru - 2010s 2018 2boys 2d 2d (artwork) alternate costume anal anal penetration anal sex animated skeleton bigger male bigger penetrating bigger penetrating smaller blue blush blue penis blush blush lines bodily fluids bottom sans bottomless bottomless male brother brother/brother brother and brother brother penetrating brother brothers clothed clothing duo ectopenis ectoplasm erection fluids fontcest formal formal clothes formal wear incest larger male larger penetrating larger penetrating smaller male male/male male focus male only male penetrated male penetrating male penetrating male mianpigui monster neck tie necktie orange blush orange penis pants pants around legs papyrus papyrus (undertale) papysans penetration penis sans sans (undertale) seme papyrus sex simple background sitting skeleton smaller male smaller penetrated suit sweat top papyrus uke sans undead undertale undertale (series) vest video games white background wqw1201501125 yaoi