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I won't post a V2 for the next assassin (would be happy if someone do it); here is a puzzle to keep you busy.
There are more blank cells than the previous JFFK, and 45 Rule becomes difficult to use here. Anyway, there is still a logical path and I whish you to have pleasure with solving it. Blank cells killers I have tried to make before are often tedious (too much combos), but this one is quite straightforward (seems to be easier than a 1.4 puzzle)

This is not a X-killer



PS code : 3x3::k:2560:1281:1538:1538:1028:2821:2821:2823:4360:1281:2560:11:1028:13:3598:15:4360:2823:4370:19:3092:21:3598:23:4360:25:1818:4370:1564:29:3092:31:2336:33:3106:1818:1564:37:1318:39:2336:41:3106:43:1580:2861:1318:47:2336:49:2866:51:1580:4149:2861:55:3384:57:2874:59:2866:61:4149:2879:3384:65:2874:67:2884:69:1606:2887:3384:2879:3146:3146:2884:2125:2125:2887:1606:





SSolver : 1.41

PS : I apologize for the bad picture quality, but I can't do a better one since I have a new computer (?)

I agree with manu that JFF5 isn't that hard though some moves might be hard to spot. But the cage design hints where you have to take a closer look so that lowers the difficulty a bit.

JFF 5 Walkthrough:

1. R123 !
a) 4(2) = {13} locked for N2
b) 17(2) = {89} locked for C1
c) ! Innies+Outies R1: 2 = R2C1249 - R1C9 -> R1C9 = (89); R2C1249 = 10/11 = 123{4/5} -> 1,2,3 locked for R2
d) 6(2): R1C3 <> 5
e) Naked quad (1234) locked in R1C23+R2C12 for N1
f) 3 locked in R3C789 @ R3 for N3
g) Both 11(2) <> 8
h) Hidden Single: R1C9 = 8 @ R1
i) Outies R1 = 10(4) = {1234} locked for R2
j) 10(2) = [64/73]
k) ! Innies+Outies R1: 1 = R2C29 - R1C25: R2C9 <> 4 because R2C2 = (34) and R1C25 can't be 6 (R1C25 <> 5; R1C5 <> 2,4)

2. R123
a) R2C9 = 2 -> R1C8 = 9
b) 17(3) = 8[54/63]
c) 5(2): R1C2 <> 3
d) Hidden Single: R1C5 = 3 @ R1
e) R2C4 = 1

3. C789
a) 16(2) = {79} locked for C9
b) Both 6(2): R68C8 <> 4
c) 11(2) @ R8C9: R9C8 <> 2,3,4
d) Outies C9 = 11(3) = {128} -> R9C8 = 8; {12} locked for C8
e) Cage sum: R8C9 = 3
f) Hidden Single: R3C9 = 1 @ R3 -> R4C9 = 6

4. R789+C1 !
a) 11(2) @ R6C1 <> 2,3
b) Killer pair (67) locked in R1C1 + 11(2) @ R6C1 for C1
c) 11(2) @ R8C1 = [29/47/56]
d) 12(2) <> 4
e) ! 4 locked in Innies R9 = 17(4) = 45{17/26} because 1,3 only possible @ R9C1 ({1349} unplaceable) -> 5 locked R9
f) 11(2) @ R8C1 <> 2
g) Killer pair (45) locked in 11(2) @ R6C1+R8C1 for C1
h) R2C1 = 3 -> R1C2 = 2, R2C2 = 4 -> R1C1 = 6, R1C3 = 1 -> R1C4 = 5
i) 11(2) @ R6C1 = {47} locked for C1
j) R8C1 = 5 -> R9C2 = 6

5. R789
a) 8(2) = {17} locked for R9
b) R9C1 = 2
c) 13(3) = {238} because {247} blocked by R7C1 = (47) -> R8C2 = 8, R7C3 = 3
d) R5C1 = 1, R6C2 = 3 -> R5C3 = 2

6. N25
a) 9(3): R4C6+R6C4 <> 4,5,6 since R5C5 >= 4
b) R6C4 = 2, R6C8 = 1 -> R5C9 = 5, R9C9 = 4, R9C5 = 5 -> R8C6 = 6
c) 11(2) @ R6C6 = [47/56/92]
d) 14(2) = {68} -> R2C6 = 8, R3C5 = 6

7. Rest is singles.

Rating: 1.25. I used IOD.

Thanks manu for another fun puzzle in this series.
Yes some were hard to spot. I got stuck for a while until I found step 10.

I'll rate JFFK5 at Easy 1.5 the way I solved it because I used a very short forcing chain. Technically that's higher rated than innie-outie differences although at a human solving level I don't think it's any harder than Afmob's step 1k.

Here is my walkthrough

Prelims

a) R1C1 + R2C2 = {19/28/37/46}, no 5
b) R1C2 + R2C1 = {14/23}
c) R1C34 = {15/24}
d) R1C67 = {29/38/47/56}, no 1
e) R1C5 + R2C4 = {13}, locked for N2, clean-up: no 5 in R1C3, no 8 in R1C7
f) R1C8 + R2C9 = {29/38/47/56}, no 1
g) R2C6 + R3C5 = {59/68}
h) R3C3 + R4C4 = {39/48/57}, no 1,2,6
i) R34C9 = {16/25/34}, no 7,8,9
j) R4C2 + R5C1 = {15/24}
k) R4C8 + R5C7 = {39/48/57}, no 1,2,6
l) R5C3 + R6C2 = {14/23}
m) R5C9 + R6C8 = {15/24}
n) R67C1 = {29/38/47/56}, no 1
o) R6C6 + R7C7 = {29/38/47/56}, no 1
p) R7C5 + R8C4 = {29/38/47/56}, no 1
q) R8C1 + R9C2 = {29/38/47/56}, no 1
r) R8C6 + R9C5 = {29/38/47/56}, no 1
s) R8C8 + R9C9 = {15/24}
t) R8C9 + R9C8 = {29/38/47/56}, no 1
u) R9C34 = {39/48/57}, no 1,2,6
v) R9C67 = {17/26/35}, no 4,8,9
w) R34C1 = {89}, locked for C1, clean-up: no 1,2 in R2C2, no 2,3 in R67C1, no 2,3 in R9C2
x) R67C9 = {79}, locked for C9, clean-up: no 2,4 in R1C8, no 2,4 in R9C8
y) 9(3) cage in N5 = {126/135/234}, no 7,8,9

A new record number of Prelims! That's because there's also a record number of 2-cell cages.

1. R5C3 + R6C2 = {23} (cannot be {14} which clashes with R4C2 + R5C1), locked for N4, clean-up: no 4 in R4C2 + R5C1
1a. Naked pair {15} in R4C2 + R5C1, locked for N4, clean-up: no 6 in R7C1

2. Killer quad 1,2,3,4 in R1C1 + R2C2, R1C2 + R2C1 and R1C3, locked for N1, clean-up: no 8,9 in R4C4

3. 45 rule on R12 6(1+5) innies R1C9 + R2C35678 = 43
3a. Max R2C35678 = 35 -> R1C9 = 8, R2C35678 = 35 = {56789}, locked for R2, clean-up: no 1,2,3,4 in R1C1, no 3 in R1C7, no 3,5 in R1C8, no 3 in R9C8
3b. R1C9 = 8 -> R2C8 + R3C7 = 9 = [54/63/72]
[With hindsight 45 rule on R1 4 outies R2C1249 = 1 innie R1C9 + 2 -> R1C9 = 8, R2C1249 = 10 = {1234}, locked for R2 is technically slightly easier than steps 3 and 3a.]

4. Killer pair 6,7 in R1C1 and R67C1, locked for C1, clean-up: no 4,5 in R9C2
4a. Killer pair 3,4 in R1C2 + R2C1 and R2C2, locked for N1, clean-up: no 2 in R1C4

5. 3 in R1 locked in R1C25
R1C2 = 3 => R2C1 = 2 => no 1 in R2C1
R1C5 = 3 => R2C4 = 1 => no 1 in R2C1
-> no 1 in R2C1, clean-up: no 4 in R1C2
5a. 1 in N1 locked in R1C23, locked for R1 -> R1C5 = 3, R2C4 = 1, clean-up: no 2 in R2C1, no 8 in R8C4, no 8 in R8C6
5b. Naked pair {12} in R1C23, locked for R1, clean-up: no 9 in R1C67
5c. 2 in C1 locked in R89C1, locked for N7

6. R1C8 = 9 (hidden single in R1), R2C9 = 2, clean-up: no 7 in R2C8 (step 3b), no 5 in R34C9, no 3 in R5C7, no 4 in R6C8, no 4 in R8C8

7. 1,7 in N3 locked in R12C7 + R3C89
7a. 45 rule on N3 4 innies R12C7 + R3C89 = 17 = {1367/1457}
7b. 6,7 of {1367} must be in R12C7, no 6 in R3C89, clean-up: no 1 in R4C9

8. 45 rule on C9 3 outies R689C8 = 2 innies R12C9 + 1
8a. R12C9 = [82] = 10 -> R689C8 = 11 = {128} (only remaining combination) -> R9C8 = 8, R8C9 = 3, R68C8 = {12}, locked for C8, clean-up: no 4 in R34C9, no 4 in R5C7, no 1 in R5C9, no 3,8 in R6C6, no 8 in R7C5, no 4 in R9C34, no 5 in R9C6, no 1 in R9C9
8b. R34C9 = [16]

9. R9C67 = {17/26} (cannot be [35] which clashes with R9C34), no 3,5
9a. Killer triple 6,7,9 in R9C2, R9C34 and R9C67, locked for R9, clean-up: no 2,4,5 in R8C6

10. 4 in R9 locked in R9C159
10a. 45 rule on R9 4 remaining innies R9C1259 = 17 = {1457/2456} (cannot be {1349} because 1,3,9 only in R9C12), no 3,9, clean-up: no 2 in R8C1
10b. R9C34 = {39} (hidden pair in R9)

11. Killer pair 4,5 in R67C1 and R8C1, locked for C1 -> R5C1 = 1, R4C2 = 5, R2C1 = 3, R1C2 = 2, R1C3 = 1, R1C4 = 5, R2C2 = 4, R1C1 = 6, R6C2 = 3, R5C3 = 2, R9C1 = 2, clean-up: no 9 in R2C6 + R3C5, no 7 in R3C3, no 7 in R5C7, no 5 in R7C1, no 6 in R7C5, no 9 in R8C6, no 6 in R9C67
11a. Naked pair {68} in R2C6 + R3C5, locked for N2
[While checking my walkthrough I spotted there is now
X-Wing for 7 in R1C67 and R9C67, locked for C67
but it’s so near the end I didn’t re-work my steps.]

12. R8C1 = 5 (hidden single in C1), R9C2 = 6

13. R9C1 = 2 -> R7C3 + R8C2 = 11 = [38/47]
13a. R7C2 = 1 (hidden single in C2)
13b. 9 in N7 locked in R89C3, locked for C3, clean-up: no 3 in R4C4
13c. R2C5 = 9 (hidden single in R2), clean-up: no 2 in R8C4

14. R3C5 = 6 (hidden single in R3), R2C6 = 8
14a. Naked pair {45} in R59C5, locked for C5, clean-up: no 6,7 in R8C4

15. 9(3) cage in N5 = {234} (only remaining combination, cannot be {126} because R5C5 only contains 4,5, cannot be {135} because R6C4 only contains,2,4,6), no 1,5,6 -> R5C5 = 4

and the rest is naked singles