Actually, no. Chloe learning about Kanna being a dragon is 100% canon. Personally, I think they're just worried that she wouldn't be able to keep her mouth shut about how amazing her best friend is.
Haru Jigokumeguri, the main character of Ojojojo. She bought out Kobayashi's company at some point prior to the start of the series and has been both seen and mentioned multiple times, though as far as we can tell she has no idea that magic exists.
@phil777 Jigokumeguri means "Tour of hells" and references the Hells of Beppu (a series of hot springs that are used for viewing instead of bathing due to their extreme heat). As for why it's named that, just read Ojojojo.
@AdamKnight
According Mononoke Sharing, she's one of the gods who created the Earth and humanity, so she is (or was) fairly high up the celestial hierarchy.