Her smile is different, so I'm sure it's a different girl. She's almost forcing herself to smile in the color images. The real Miyu had a big silly grin, while this one seems tense or forced. Not that she's not happy sometimes, but that she's in pain. At first it seemed like maturity, but now it sticks out too much. Her love of taiyaki is extreme, so I'm not sure if it's forcing a character or showing something distinct anymore
She's definitely going to kill that bully. If Miyu wouldn't have died if Yuushin showed up on time, and she's supposed to act like Miyu's avatar, that boy indirectly killed Miyu. He must die for justice to be served... is exactly the sort of logic to expect.
So far I'm guessing the heroine was forced by her current mom (Miyu's mom) to mimic her dead daughter. Miyutoo may have been uncomfortable comparing the boy's mother to her own. Miyu's father would have been telling the truth. And if she moved in it's with a parent, and instead of feeling emotionally distant to a mom it's more likely the mother we only saw in a photo is currently raising this Miyu in an old home. Both parents are characters, we only know one had a caring moment and one was painted as distant.
I could be wrong though, and she's like a zombie, or the father was lied to about her death so mom could escape or abduct her, or something. Pretty sure this is a new person with her own backstory though. She can be seen, is properly enrolled in school, is going to greet mom
