This single was released in what I call a difficult week. There were only two other releases on the same date for a reason. It is just after the busy end-of-year period with many music shows. At the time when everyone is looking back at the hits of the past year it is difficult to introduce a new song to the general public. I think management knew this and thought it was a good time for a little experiment with the Airi solo. The traditional H!P concerts at the start of the new year are a great time to target this single at the main group of potential buyers. The signed poster lottery certainly helped to lure them in. But the general CD buying audience is not reached as much. As a result this single is one "just for the fans".
Just my 2 cents.