The thing is, I feel like he ended up growing out of his crush towards Aoba, and his second love is what he chose in the end. They were more on equal footing, him and Ikkei, and they both grew into happier people together. I think this is why Ikkei is definitely not a rebound. Especially because we can see that Miki was also slowly moving on from Aoba. He grew into a more confident person who was getting into less fights and is able to make his own decisions. Have his own friends. Etc.
It isn't toxic at all since both of them are honest, they communicate with one another, and they both genuinely care about each other's well-being. This is the definition of healthy to me!
story's good but i kinda hate how aoba had such a big a$$ manipulator vibes (he was such a dick) and dk abt hara but it felt like he was comflirting miki then eventually became a rebound (it just kinda felt toxic to me, but ig the relationships are just represented well enough to be kind of like in real life rs? anyways, this is all just fiction so meh)
again, this was just my tots alone but yeah the story alone is cute!