Selyra

I don't mean to make this intentionally difficult to figure out, but unfortunately those aren't the song either... They fit my description nearly to the dot, but I can tell they're not quite the song I'm looking for. I'm surprised how many songs sound similar to Let Her Go. The third one you listed was close, but the singing is not that much louder than the music, and it's not quite that emotional. The second video has singing that sounds remarkably close to the song I'm thinking of. I wish I could be more specific, but I wasn't offered enough time to learn more about it. Ironically, the first 40 seconds of the first song sounds the closest out of any guess so far. The rhythm is the most similar, but it's still not quite it. The singing is quiet for the first 40 seconds, and the voice is similar. But I'm pretty sure the target song is sung in English, and the target song basically stays mellow through the whole thing. That first one has moments where it picks up. And remember, the target song has a part referencing a hall or hallway.

EDIT: I'd hate to pack all the effort onto you. It would help a lot if more people were in on this one.