what is the vocaloid song the riddler who can't solve riddles about ?

[junjouromantica]

ok so i watched the video for the riddler who can't solve riddles and the other part the riddler who won't solve riddles by vocaloid rin and len but can someone tell me what the song is about what is the story of both the songs ? i got a bit confused when i listened to both of the song can someone help me thank you