This went pedo too fast, this has the potential to be a great bittersweet "cuteness overload" but went full weird suddenly from chp 2 onwards, I know it's not explicit, but given japanese mentality and their behaviour around kissing he's going all out flirt mode with the demon, no inner battle in regards to her being a kid, no wondering what the right course of action may be, just start kissing right from the first innuendo. That not only makes the story predictable and repetitive but also takes from the true beauty of this genre and makes it awkward. Yeah, he may call it teasing but it's teasing a kid, he goes as far as cancelling the date, does it mean he's aiming for the demon? If not then it's as simple as to explain that she's invited even if he has a GF (logically he'd be with somebody as understanding as him). Or is he waiting for the demon to grow while messing around? Sincerely it's quite an abrupt development that should be left for hentai, manga has to explore different ends. . . [And don't come saying that it's another culture represented on the manga, we all know that your own culture sips in and shapes your work, more so on things like manga or so I've seen from years and years of reading]