I personally dont think it is wrong to make sexual content of undertale characters unless they are minors. If the character is a minor, aged up or not, their shouldn’t be any sexual content. But if its an adult character like sans or undyne, I think its ok to draw things like NSFW and write smut. What I dont like is when they take a character and make them sexual in every context: Ex: Drawing toriel with large unnaturally large boobies or just making sans allways sexy 💀