>>55285050i'm partial to okayu's covers but this one definitely isn't better than the original. it's not that okayu's pitch doesn't work, but her voice is too low-energy for the melody, so it doesnt give the same feel the original has at all.
i thought this cover was quite good compared to the original when i listened to the original afterwards. after having listened to both a lot, i think they're both good, but okayu's cover is still incredibly solid:
https://www.youtube.com/watch?v=QkQ5SfZ0YlM