I play Tager, and I've got a pretty good idea of what works for Nu against Tager because of that. (So many Nus online. -_-) A lot of this has been mentioned before, but anyway:
At the beginning of the match, you probably want to get away from him with a backdash or instant air backdash. Nu's backdash is good and quick and I can't think anything of Tager's that can reach you before you recover. Once you've built up some distance, poke with lone 5Ds or 5DD. If he blocks, go ahead and add some followups like 236D to chip away at him and push him further away from you. For that reason, you'd probably like to avoid 236D~C, since that actually pushes him closer to you. Anyway, if he sledges, backdash and throw out 5DD again. If he did an A sledge, he might be able to recover and block or even B sledge, so watch out for that and respond appropriately. If you hit, finish up with the rest of that 5DD 4DD 236D BnB.
If he jumps in, catch him with 6DD or 2DD if you can, or backdash if you can't. Keep him off of you by either backing away or using your swords to push him away. If he ever pins you in the corner, use Act Pulser to get past him.
Be careful with Act Pulser though... DO NOT Act Pulser into his throw range. Against a lot of characters, Act Pulser into melee range can be a great mixup option. Against Tager, it's basically just a way to eat a free 360A. Make sure your Pulser will get you well past him or you're looking for some serious pain.
That's basically it, really. It's slow and painful for everyone involved, but it should get the job done as long as you've got the reactions for it.