Here's some info about the new songs from her LINE account, that wasn't posted yet:
WickedGirls is a song about a woman's daily life.
insane is like an attacking Koda Kumi. She's rapping in it, what she hasn't done for a long time.
Promise you is the first song she wrote for her own son.
Heartless is the song with the single piano and it's about times, when we're having negative thoughts.
I also translated the lyric snippets of the rest of the previews roughly, so that you can get a grasp of it, if you can't read it yourself: