Only the 'good' endings use a 'happy' post-credits CG.
Also, I liked Mizuha's route. A classic story of an uptown girl (whose life is defined by her status) and a normal guy (who helps her navigate it for the better).
Can someone explain a bit what happens in Mizuha route please? I've been stuck with the teacher, the blue haired girl and the loli but I couldn't unlock the rest of the routes no matter how many times I finished those 3 routes...