ThatOneLevel # 2 - Amala Temple
For the Black and Red Temples, I provided a video guide:
https://www.youtube.com/watch?v=wpvpmVWSTI8
You can explore if you want, but that's up to you. This is just a way to show you the correct path.
For the White Temple, refer to this map:
http://www.gamefaqs.com/ps2/582958-shin-megami-tensei-nocturne/faqs/49801
I strongly recommend taking the small detour to get the Blessed Fan. You don't need it, but it sells for 50000 Makka. If you're playing on Hard Mode, that's invaluable.
If you're having trouble with Aciel, he'll be in the next entry which I will post tomorrow.