Yu Narukami has a very basic approach to oki that focuses on utilizing meter to create safe jumps with his Cross Slash or meaties with his EX Zio. If his Skill Gauge is low, he can use assists that generate knockdowns at the end of combos to set up safe jumps. If no resources are available, almost all his combos will end with B Swift Strike, which has enough of a frame advantage to meaty with his 5A.
0) Raging Lion (j.C): Not directly an oki option, however it allows Narukami to end air combos with ground specials and supers, which is vital to his oki game.
1) Swift Strike (214A/B): Works anywhere on the screen. Weakest oki option, but requires no resources.
2) EX Swift Strike + Big Gamble (214C~A/B/C): Works anywhere on the screen. Deals minimum damage and has excellent corner carry but costs one bar.
3) EX Zio (236[C]): Works anywhere on the screen. Deals minimum damage but costs one bar.
4) Cross Slash (214B+C): Works anywhere on the screen. Deals minimum damage and sets up a safe jump but costs two bars.
Choosing an Oki Route
0) Raging Lion is the key to all of Narukami's oki as it can be used to end any air combo with grounded moves as it is special and super cancelable on hit. Avoid using air Big Gamble and Ziodyne as they don't provide any oki and can't combo into Raging Lion. If Narukami is already on the ground, his sweep (2C) fulfills the same role.
1) Swift Strike is Narukami's go-to combo ender for all his resourceless combo routes. No fancy set-ups here, just a meaty normal, likely 5A, to pressure the opponent's wake up.
2) EX Swift Strike into the Big Gamble follow up provides better damage, corner carry, and frame advantage than the normal version. It also is the only move that can combo after certain moves such as max range 5B and counter hit Zio. Provides empty jump-in safe jump, which makes it good for throwing in an empty jump-in low.
3) EX Zio is Narukami's most complex oki tool. After landing Raging Lion, make sure to touch the ground before inputting EX Zio, otherwise the move will be too high up and won't threaten the opponent's wake up. Hold C to charge the Zio and release so that it meaties the opponent or hold longer so that Narukami can apply high/low mix ups (such as with the normally unsafe Raging Lion) while Izanagi covers him and launches opponents on a successful hit. This set-up is reversal proof as Narukami can block while Izanagi both attacks with Zio and defends with his body, though not that invincible throws will still catch Narukami. Note that if Izanagi is hit, the charge will end and Narukami will lose 5% of his max health. Costs 1 bar and incurs a 180 frame meter build cooldown, so use carefully.
4) Cross Slash is both Narukami's most damaging combo ender and his easiest to use oki tool. Simply IAD after the super to use the impressive frame advantage to create a safe-jump. If the opponent techs forward, Narukami must IABD to cover it. Can be used at the end of essentially every combo and can even be done after a partner's super through the use of Distortion Skill Duo. Very strong and oppressive oki overall, though note that this super costs two bars and incurs a 180 frame meter build cooldown.