Xbooru - 2010s 2016 2boys 2d 2d (artwork) animated skeleton ass bent over blue ass blue body blue butt blue hoodie blue jacket blush bottom sans clothed/nude digital media (artwork) drooling duo ectobody ectobutt fire elemental from behind position glasses glasses only grillby grillby (undertale) grillsans heart hoodie humanoid jacket male male/male male only monster monster boy orange body penetration penetration from behind sans sans (undertale) seme grillby sex sex from behind simple background skeleton third-party source top grillby trembling uke sans undead undertale undertale (series) unknown artist unknown artist signature video games white background yaoi