Woah! This is really nice! They talk too much and too eloquently for normal conversation, but ah well. Lots of manga do that. XD
Is Dion's dream just to help humans in general, or does he have a specific sort of help he wants to give? You've offered a lot of background (a bit obviously dumped through the characters, but it's okay) as to the prejudice against blood mages, but how entrenched is it, and how long has it been around? Surely there's someone out there who doesn't buy into it so much. If there aren't a lot of blood mages left, then there are always those people who don't believe something unless they see it (gen a bad thing, but I guess a good thing here). Will they meet someone like that at one point?
Wherever are their parents? (They feel like cousins or something to me, but maybe blood magehood isn't genetic. How does it pass on?) Are they related? (With that blush, probably not, but I still want to ask.) If it's not genetic, who brought them into blood magehood? And also if it's not genetic, why haven't they considered getting out of blood magehood? (There's only so much two people can do, but people have powerful abilities to forget when you give them time. Their descendants might be better suited if someone on the brink of death is running away. I mean, he was going to die anyway, why wouldn't he try those two?) Does anyone know why the original blood mages (behind the bad rep) started harming people? Surely they weren't just instinctively evil, unless of course it's something they have to do...?
Of course, this is the first chapter. You haven't had time to really introduce us to things yet (and if I had one piece of advice, it's okay to space out your world-building instead of pouring it into character dialogue! Readers are less impatient than you think!). I might think of more questions as we go on, but I do want to apologize a bit if this comes off as overwhelming. XD I don't normally write like this here, on Mangadex, but I did want to be helpful. Bye!