The Tensei Gotoki de Nigerareru to Demo, Niisan? manga concludes abruptly around chapter 20, where the yandere sister theme returns for a final confrontation. It is widely considered to have been cancelled early because it skips major plot points from the original light novel.
Was Do You Think You Can Run After Reincarnating, Nii-san Axed? The Tensei Gotoki de Nigerareru to Demo, Niisan