Xbooru - 2010s 2016 2boys animated skeleton black hair blue eyes boots bottom sans bound wrists clothed collar collar and leash heart hoodie humanoid humanoid robot ifuckboxppl leash leash and collar leash pull licking lips male male/male male only mettasans mettaton mettaton ex pink boots robot robot humanoid sans sans (undertale) seme mettaton simple background skeleton straddling top mettaton uke sans undead undertale undertale (series) video games yaoi