Xbooru - 2010s 2016 2boys 2d 2d (artwork) animated skeleton anon anonymous anonymous male blue tongue bone bottom sans digital media (artwork) disembodied penis duo genitals grey background licking licking penis male male/male male only nubs oral penis safetytrance sans sans (undertale) sex simple background skeleton solid color background solo focus text third-party source tongue uke sans undead undertale undertale (series) unseen character unseen male face video games yaoi