hi fellow english viewers! im wee woo! i am currently learning japanese (im still a novice though, so take my comment with a grain of salt) i thought i'd explain the plot of the song for the english viewers! you've been in an accident, and you were knocked out. you wake up in a world other than ours, where you have the choice between life and death. the people singing are like your guardian angels, or "spirits" as i will call them. your "spirits" are both urging you to hold on to your life, but also saying it's okay if you have to go. throughout the song you slightly fade in and out of consciousness. during the quiet parts of the song, you hear a ringing and the sound of exhaust. this is because you are fading back to consciousness, but your "spirits" begin singing again. at the end of the song, the siren and exhaust becomes more apparent, as you've finally woken up. the giggle isn't entirely explained, but my interpretation is that your "spirits" are wishing you well as you chose another chance at life. sorry if that was a lot to read! again, since im still new to learning japanese please take this comment with a grain of salt! i hope you enjoyed!