Sorry this is late.
Anyway, Narukami has a really strong oki game and blockstrings that can lead to overheads -> more damage. A lot of time will be spent blocking if he knocks you down, so you’ll just have to get used to individual blockstrings and tendencies.
As Yukiko you can’t get too complacent with throwing fans, cause you’ll eat Persona-carts, and jumping in on him is dangerous due to his 2B. You can control space with single fan throws and maragis at range, just be wary when he has meter cause he can punish a lot of things on reaction with Persona-carts or super.
You have to be very careful about your blockstrings when he’s in awakening, since if they aren’t tight you could eat a crossslash. 5aa is safe, but followups can be interrupted, so jumpcancelling is an option. Ideally you catch him at max range 5aa, then jumpcancel if you need to; if you’re too close he can just DP you as you jump.
If you block Narukami’s DP, be aware that he can cancel to super before he lands or when he lands, so if you intend to punish and he has meter, it’s safer to run behind him and 5b (counterhit) 236D and lead into stuff.
A lot of newer Narukami’s like to throw out 5d randomly in a blockstring. If you see Narukami throw his hand out and has Izanagi plant his weapon in the ground, it’s not safe; you can sweep, 236B him away, or go for a bigger punish if you’re closer.
Other tricks include Ziodyne OMC (100 meter), then he can mix you up while you’re getting hit by the lightning. You always have the option to counterassault the followup, which will get you out, but if he baits it you get hit.
If a Narukami does C Ziodyne (the fast one), you can punish it anywhere on the screen with 6D after you block it. It’s also free instant block food, so you can mash back all you want while you block it.
Grounded Raging Lions (the overhead) are safe on block against Yukiko, and at advantage if Narukami uses the B or SB version, so try not to stick limbs out too often, otherwise he’ll catch you with his faster buttons.
It can be a tough matchup, especially when you’re first starting out since there are situations where you will be forced to block. A lot.