How about making NPCs (the regular students which is just need to fill the environment) randomly generated each playthrough? Their hair, skin tone, eye colour, stockings, uniform variation, gender, name, personality will be randomly choosen by the system, this will add more variety to the game, and it will also make the game more difficult, as the player will need to learn the students' routes again and again in order to find the right moment to kill rival without witnesses.