First, write it as KISS x KISS = PASSION. We can also note that since PASSION is only 7 digits (<10,000,000), K can only be 1,2, or 3. Note also that as PASSION is square, the ones digit N can only be 0, 1, 4, 5, 6, or 9. Further, as N is the ones digit of SxS, N cannot be 0 of 5 (as that would require N=S). So N is 1, 4, 6, or 9. Each of these gives limited possibilities for S (N=1 -> S=9, N=4 -> S=2 or 8, N=6 -> S=4, N=9 -> S=3 or 7).
Try to proceed from there.