Kanojo ga Flag wo Oraretara

"I think... the flag was... probably raised already at that time." - the way that line at the start of the series read, it makes me think that the "flag" he's referring to is one that guides the whole series.
In other words, by stopping that accident and getting involved with Nanami, everything that happened afterwards had already been set in motion. Nothing that he could do would change the way things turn out between them at this point. Maybe later we'll see flags for her, but it seems like, based on her and his personalities, there aren't any options right now, like with the other girls, to change events involving Nanami. She is going with the flow to an extent, but she would stick to him no matter what he said, simply because that is the type of person she is.
To put it in the most cliche way possible, the wheel of fate has been set in motion, and he can't change that.
>_> Did that make any sense, or did it seem like idiotic babbling from an arrogant overthinker?

she knows there won't be any flag from her, as well she notice that he look above their heads before he responds

sleep over flag