Yeah, it's hard to know why for sure. I personally love No Regret and just like Marurosu, it was my first Kumi song thanks to Maeda Ken performing with HINOI TEAM. lol
https://www.youtube.com/watch?v=X2ME-lTit4g
The Bold & Delicious performance is awesome as well. haha
The whole 12 singles was a very successful project. Not only the singles sold well enough with two of them being #1, the album compiling the singles almost selling 2 million copies.