That's one compelling "story-in-a-storygame" supported by a beguiling soundscape.
Or is it just a straightforward "sad secret love" story ? Curious questions arose in my mind after I researched the Japanese supernatural allusions in the game ...
Is the schoolgirl protagonist an Oni (おに) worshipper ? Or could she instead be an Oni disguised as a schoolgirl, thus her/its habit of walking the rural lanes after sunset ?
The latter possibility imparts to the game an unexpected (& intriguing) dimension that leaves me feeling half-glad that the boy didn't look out of the window -- but also half-disappointed that he didn't look out of the window, because I'm now curious know what this somewhat unusual Oni really wanted, & also who it was before it became an Oni.