Based on the sarcasm comment I'm assuming that wasn't even close to Kases best time since nobody mentioned a new best time to her either so maybe she really knew she had nothing to worry about since and racing was just the easiest option idk maybe
What I dislike about different mediums dealing with curses/the supernatural is there's almost never a satisfying conclusion. Neither we the readers or the characters get an explanation as to the reason any of this happened. Even their hypothesis doesn't make any sense since being resuscitated is pretty common. I can never enjoy these types of stories when so much is left unnecessary unanswered. I'd give this a 5.5/10
I know its childish of me but I went from liking this manga to disliking this with Natsukis death. (Based on the tags I know I should have expected this) Something about killing honest and genuine characters really upsets me even more so if those 2 in that occult research survive this.