Who the heck was Kosagi?? Some of the lines (in the Eng dub at least) seem to imply she was someone that knew Karasu/Yuu since they were younger. At first I thought she was Miho, but she showed up in the last episode. Was it possibly ANOTHER version of Miho due to convergence in La'Cryma before Haruka stabilized that dimension?
And for that matter, how did Miho become blind in La'Cryma? That one seemed to come out of nowhere.
Kosagi was probably just someone Karasu made friends with shortly after the La'Cryma. Future Ai! did mention that there was a gap of at least five years. So anythings possible really.
Miho's blindness could be explained by the implication that the Bad Future shown to Haruka in episode 22 is La'Cryma's past - Fukuro retains the scar he received after losing an eye in the knife fight, which further supports this. Miho, in turn, could have survived her suicide attempt by overdose, but was left blind as a result.
It is established that the The Dragon Knights are the only ones who can travel between dimensions because they had their bodies extensively manipulated on a quantum level. So how come they manage to take normal people with them, like Haruka and Yuu, without any ill effect whatsoever?
This has been explained in the anime. When Haruka goes to La'Cryma for the second time with Yuu, his existence is in danger because of how La'Cryma was built on some quantum...stuff. Haruka was a special case, as Ai explained.