Undertale clearly is a ripoff of Len’en. The most obvious proof for this is the fact that the main character and many other characters of Undertale are “oh, what a coincidence” without defined sex. How high do you think is the chance for this to be just a mere coincidence. Well, I am not finished yet. You see there are many big and small hints in the game. Consider the fact that that the child easily got into the underworld, but it is hard to escape from there, just like JynX described the Mugenri Barrier. Or the role, Skeletons play in the game. Almost at the start of the game, you meet a Skeleton (or two in undertales case) which at the beginning may seem weak, but at the very end of the game turn out to be one if not the strongest character in the game. Just like Mugenri, the underground is ruled by two beings, of which one is currently not an active ruler. When in Len’en Tsurubami leaves Mugenri in Evanescent Existence (which can be seen as the beginning of the actual story), in Undertale Toriel returns to the palace at the end of the game. Not to mention that it messes with timelines. Of course, I could go on and on for hours about this, but I think if you aren’t completely unaware, you should get the point. Undertale is a ripoff of Len’en. This also means that all self-proclaimed “Undertale-Fans” are actually Len’en-Fans, who are simply not aware of the existence of Len’en.