Nanami Knight Braidfield??? Like, I guess that's a name...
Anyways, it seems fairly likely that he's unable to see her "flags" for whatever reason. Hence why he didn't notice that she was going to die until the truck was literally right in front of her. And why he doesn't seem to notice that she's obviously in love with him. The intro also has him being unsure about the specifics of her "flag."
I hope this reveal is repeatedly put off until the end of the series for no good reason, because it'll be kinda embarrassing if it happens in chapter two.