[Devil Doll]

Originally Posted by houkoholic

Think of that in the same way as why Ayu roams the shopping district, why Mai goes to the school at night, why Makoto became what she is etc.........

When this series began Nayuki was able to run to school faster than Yuuichi (she's the captain of the track&field club after all). Now we see her sleep on her way to school, and sleep at class. Yuuichi keeps supporting Mai and should have less sleep than Nayuki. Mai was hunting demons the whole time, but something changed about Nayuki...

Spoiler for Nayuki's role in Kanon 2002, plus a speculation:

Could she be following him at night and know about the whole Mai story? Given her own issue she would have a very valid reason for doing so.

As for the cultural issues of Yuuichi's behaviour, I can accept that. There are anime characters of that type, for example in Meine Liebe - then again they're supposed to be Europeans.