Ooh, right up my alley.
Even though her supers really aren’t all that great or too terribly useful, K is a good groove for her because of her low stun. Just as you’re about to get stunned, you usually go into rage, which will usually make the other guy back off enough for you to gather yourself.
However, the danger with using her is that it’s really easy to get killed. If you make one mistake, you’re likely to die with one good combo which will put you into stun, which leaves you wide open.
That said, Nak has two tools that you really need to milk to get the most out of: Her speed and Mamahaha, her hawk. You need to change up jumps, small jumps, super jumps and bird mounts (qcb+k) to confuse the heck of your opponents. Use bird monuts to give the other guy a false sense of security, then go in for the occasional empty jump to throw or low combo, and of course mix that up with roundhouse kicks, her only really good jump in attack.
When you decide to mount Mamhaha, you need to change up your game there, too. Immediately dismount via a regular spinoff (fierce while mounted) to give the illusion of a regular jump, or the bladed spinoff (roundhouse while monuted) which is safer and if they are closer to you. You’ll also need to mixup how long you stay on Mamahaha, from quick-off to staying on the whole 7 seconds, including moving around on the bird both really high and really low, poking out attacks to let them know you’re not 100% vulnerable, etc.
Your other Maha dismount options are the fireball (qcf+p while mounted), which is very slow, and the mutsube (qcb+p while mounted), which is lightning fast. Use them to nail jumping and crouching opponents, respectively.
Of course, in using K-Groove, you are relatively safe in the air thanks to Just Defending, but it goes without saying that you shouldn’t jump around too much. This is where Nak’s speed game on the ground comes into play.
Nakoruru is so fast, she can always be next to a knocked down opponent after any move she has, thanks to her Flash Gordon run speed. In a run, a great move to turn the run into is her command flipping slash (df+fierce). It stays out for a pretty good amount of time, has great priority, and can stop crossups and squash wakeup attacks. You can also use c.roundhouse, which stays out a bit longer than it appears to as well. She also has awesome air coverage with Mamahaha when he goes in for a fire dive (hcb+p). Using these two tactics, you can pin down opponents easily (though be careful if they have a bunch of super meter), which gives you a monumental advantage.
Once you’ve got them cornered or otherwise in distress, you can start using Nak’s supers. Really, the only one you’ll be using in K-Groove is the Mamahaha Fireball super (hcbx2+p), since it’s virtually 100% safe, as you can throw it out from anywhere not needing to worry about retaliation. It’s also free chip damage, or a throw if they decide to roll through it. The easiest way to combo into it is to jump-in with a roundhouse kick and have the super come out when you land. You can also use it to punish anyone jumping in at you, but make sure you wait until they’re starting to come down from the jump so it’ll hit them instead of going under them.
Her combo super (hcbx2+k) and healing super (qcfx2+k, 3K to cancel) are really only good if the other guy is stunned, since you need an ungodly amount of time to pull them off and be useful.
Overall, the trick with Nak is to keep the other guys from abusing you by pinning them down, come in for an attack when you’re confident you can do it relatively safely and with confusion on your side, keeping them from trying anything funny when they get up off the ground, then punishing them when you can get a good lick in with a super or when they try jumping into when you have rage on the ready. Use your speed and Mamahaha to your advantage, as those are the only two advantages you have with her.
