more voice acting, new major characters, new scenes / scenario, new area with story arc, dating feature with the majority of major characters, new endings with a choice of who end with, new monster ranch area with a dog park section, some few new scenes around town with npcs, new ones, old ones (for example your neighbor, red haired girl outside your home), tons of new scenes and scenarios (h-scenes) with art and new voice acting, new mobs and bosses with new attack patterns, etc etc...
In terms of just text alone, the total text in append is about a good 80-85% the size of base, so it essentially doubles content in terms of story alone