[Does it make it better if he found out he was one of the affected? That might be why he didn't catch the little hitch in how today has felt off. Honestly, if asked Ai might tell him he was changed in her point of view - as was Ichiru. Though she wouldn't say how. Maybe just a few changes and then tell him to come back tomorrow to continue that conversation.]
No, it's not unheard of. Vampires and hunters alike go to great lengths to make sure that memories won't be questioned. That is the point in changing them, after all.
[Her theory is that the maintenance is the reason behind the changes. Which is why she's attempting to research it with little to no success. Ai might be comprehending the material she's reading but none of it helps support or deny her theory.
Of course she's expecting it. The second question makes her frown.]
Yes, they became vampires overnight. There are at least three as far as I can tell. Since no one is panicking over the change I can only assume that they believe they've been vampires. [Hard to say when she actually hasn't talked to any of them yet.
A shake of her head.] I'm afraid I don't know enough people to notice any other physical changes.
[Except for you. Again Ai does a good job of not letting her eyes move to his neck.]