This puzzle if a Killer-X and non-consecutive horizontally and vertically.
Prelims
a) R2C23 = {15/24}
b) 9(2) cage at R2C7 = {18/27/36/45}, no 9
c) 8(2) cage at R2C8 = {17/26/35}, no 4,8,9
d) R3C23 = {29/38/47} (cannot be {56} NC), no 1,5,6
e) 11(2) cage at R7C2 = {29/38/47/56}, no 1
f) 12(2) cage at R7C3 = {39/48/57}, no 1,2,6
g) R7C78 = {18/27/36} (cannot be {45} NC), no 4,5,9
h) R8C78 = {59/68}
i) 19(3) cage at R1C3 = {289/379/469/478/568}, no 1
j) 11(3) cage at R1C8 = {128/137/146/236/245}, no 9
k) 19(3) cage at R3C4 = {289/379/469/478/568}, no 1
l) 11(3) cage at R6C6 = {128/137/146/236/245}, no 9
m) 19(3) cage at R8C1 = {289/379/469/478/568}, no 1
n) 11(3) cage at R8C6 = {128/137/146/236/245}, no 9
o) And, of course, 45(9) cage at R3C5 = {123456789}
1a. 45 rule on N1 2 innies R1C3 + R3C1 = 13 = {49/58/67}, no 1,2,3
1b. 45 rule on N3 2 innies R1C7 + R3C9 = 17 = {89}, locked for N3, clean-up: no 1 in 9(2) cage at R2C7
1c. R3C9 = {89} -> 15(3) cage at R3C9 = 8{16}/8{25}/9{15}/9{24} (cannot be 8{34} NC), no 3,7,8,9 in R4C89
1d. R1C7 = {89} -> no 8,9 in R1C6 (NC)
1e. 45 rule on N7 2 innies R7C1 + R9C3 = 3 = {12}, locked for N7, clean-up: no 9 in 11(2) cage at R7C2
1f. R7C1 = {12} -> 15(3) cage at R6C1 = {59}1/{68}1/{49}2/{58}2 (cannot be {67}2 NC), no 1,2,3,7 in R6C12
1g. R9C3 = {12} -> no 1,2 in R9C4 (NC)
1h. 45 rule on N9 2 innies R7C9 + R9C7 = 7 = {16/25/34}, no 7,8,9
2a. Hidden killer triple 1,2,3 in 15(3) cage at R1C1, R2C23 and R3C23 for N1, each can only contains one of 1,2,3 -> R3C23 = {29/38}, no 4,7
2b. Killer pair 8,9 in R3C23 and R3C9, locked for R3, clean-up: no 4,5 in R1C3 (step 1a)
2c. Hidden killer triple 7,8,9 in R7C78, R8C78 and 15(3) cage at R8C9 for N7, each can only contains one of 7,8,9 -> R7C78 = {18/27}, no 3,6
2d. Killer pair 1,2 in R7C1 and R7C78, locked for R7, clean-up: no 5,6 in R9C7 (step 1h)
3. One can invoke symmetry because all the corresponding 2-cell cages sum to 20, the 3-cells cages to 30 and the 45(9) cage is symmetrical about the centre of the grid -> R5C5 = 5, placed for both diagonals, clean-up: no 1 in R2C3, no 3 in 8(2) cage at R2C8, no 7 in 12(2) cage at R7C3, no 9 in R8C7
3a. R5C5 = 5 -> no 4,6 in R46C5 + R5C46 (NC)
3b. 9(2) cage at R2C7 = {36/45} (cannot be {27} which clashes with 8(2) cage at R2C8), no 2,7
3c. 11(2) cage at R7C2 = {47/56} (cannot be {38} which clashes with 12(2) cage at R7C3), no 3,8
3d. 11(3) cage at R1C8 = {137/236/245} (cannot be {146} which clashes with both the other cages in N3)
3e. 2 of {245} and 6 of {236} must be in R1C9 (NC) -> no 6 in R1C8 + R2C9, no 4 in R1C9
3f. 19(3) cage at R8C1 = {379/478/568} (cannot be {469} which clashes with both the other cages in N7)
3g. 4 of {478} and 8 of {568} must be in R9C1 (NC) -> no 4 in R8C1 + R9C2, no 6 in R9C1
4a. R2C23 = [15] (cannot be {24} which clashes with R3C23 using NC), 1 placed for D\, no 2 in R1C2 + R2C1 + R3C2, no 6 in R1C3, no 4,6 in R2C4 (NC), clean-up: no 8 in R1C3, no 7 in R3C1 (both step 1a), no 9 in R3C3, no 7 in R3C7, no 4 in R3C8, no 6 in R7C2, no 8 in R7C8
4b. R8C78 = [59] (cannot be {68} which clashes with R7C78 using NC), 9 placed for D\, no 8 in R8C9 + R9C8, no 4,6 in R8C6, no 4 in R9C7 (NC), clean-up: no 3 in R7C3, no 3 in R7C9, no 2 in R9C7 (both step 1h)
4c. R1C3 = {79} -> no 8 in R1C24 (NC)
4d. R3C1 = {46} -> no 5 in R4C1 (NC)
4e. R7C9 = {46} -> no 5 in R6C9 (NC)
4f. R9C7 = {13} -> no 2 in R9C68 (NC)
4g. 7 in R3 only in R3C456, locked for N2
4h. 3 in R7 only in R7C456, locked for N8
5a. 15(3) cage at R1C1 = {249/267/348}
5b. 2 only in R1C1, 8 of {348} must be in R1C1 (NC) -> R1C1 = {28}, no 8 in R2C1
5c. 15(3) cage at R8C9 = {168/267/348}
5d. 2 of {267} must be in R9C9 (NC), 8 only in R9C9 -> R9C9 = {28}, no 2 in R8C9
5e. Naked pair {28} in R1C1 + R9C9, locked for D\, CPE no 2 in R1C9, no 8 in R9C9
5f. R3C3 = 3, placed for D\, R3C2 = 8, R3C9 = 9 -> R1C7 = 8, R1C1 = 2, R7C7 = 7, placed for D\, R7C8 = 2, R7C1 = 1 -> R9C3 = 2, R9C9 = 8, no 2,4 in R3C4, no 7,9 in R4C2, no 4 in R4C3, no 6 in R6C7, no 1,3 in R6C8, no 6,8 in R7C6, no 3 in R9C2 (NC), clean-up: no 6 in R23C7, no 4 in R78C3
5g. R3C8 = {56} -> no 6 in R2C8, no 5,6 in R4C8 (NC)
5h. R2C8 = 7 -> R3C7 = 1, both placed for D/, no 2 in R3C6 + R4C7, no 6 in R3C8 (NC)
5. R3C8 = 5 -> R2C7 = 4, R1C8 = 3, R1C9 = 6, placed for D/, R2C9 = 2, R7C9 = 4, R9C7 = 3, R8C9 = 1, R9C8 = 6
5i. R56C1 = {37} -> R6C8 = 4 (cage sum) -> R56C1 = [37] (NC), R4C89 = [15]
5j. R7C2 = 5 -> R8C3 = 6, no 6 in R6C2, no 4 in R8C2 (NC)
5k. R8C2 = 3 -> R7C3 = 9, R9C1 = 4, all placed for D/, R9C2 = 7, R8C1 = 8, R23C1 = [96], R1C2 = 4, R6C12 = [59], R45C1 = [37], R4C236 = [682]
5l. R9C7 = 3 -> R89C6 = 8 = [71]
and the rest is naked singles, without using NC or the diagonals.