Here are some more updates on Junsu (XIA)'s solo comeback, which we know you're dying to find out! He's confirmed his title track to be a ballad song titled "Had To Be Yesterday" (literal title)!

C.JeS Entertainment stated, "The title track for XIA Junsu's mini-album has been confirmed to be "Had To Be Yesterday". The title track "Had To Be Yesterday" has a lyrical ambience and its melody and lyrics are emphasized by XIA's emotional voice. We've finished preparations for his ballad track to make its mark this autumn."
Famous singer-songwriter Lucia composed and wrote Junsu's the song. This is also Junsu's first ballad song for a title track, so we're more than looking forward to it!
Stay tuned for his mini-album release on October 19!