The song has a stronger, more upbeat sound than title song "Spring Day", and the MV definitely matches that mood. 

"Not Today" is one of the 4 new tracks on 'WINGS' epilogue, 'You Never Walk Alone'. The other tracks are title song "Spring Day", as well as "Outro: Wings", and "A Supplementary Story: You Never Walk Alone". 

Check out the new MV above and below!