Nagi: refers to the snake (Naga) in Hinduism, which are supposed to be evil god like creatures that are the enemies of the Garuda, which is a bird-like creature
Takayanagi: Taka, which means A hawk or falcon, but also means a number. Ya is the number eight in japanese. Nagi like before, refers to the snake again. So, the most logical meaning of his last name means the Eight Headed snake.
Natsume: Its some type of tree, forgot the actual name of the tree though, which is probably why Maya can use wood ki.
Makihara: I think this is a pun off of Bob. Maki means volume, like in music, while Hara can mean "moor". However, Ma means space/time/ purity. Ki, as we all know is life force, breath, etc. Hara can also refer to the Dantian in martial arts where all of the Ki is supposed to be stored in.
Kago: Divine protection, a cage, or a mistake. The divine protection fits with Souhaku's buddhist/taoist powers. I also took a cage into assumption because he is keeping his ultimate warrior in a "cage", restraining him; having control over his ultimate warrior until he feels the time is right. A mistake because he is probably going to make a mistake about something in the future.
Tawara: Straw Bag.....yeah.....
Anyways, I was bored and needed something to do to fill up my TenTen withdrawl, waiting for 105 to come out. Since most mangas always gives away the character based on names, especially their last names, I just did a little research on each of the main guys last names. From what is shows, it sounds like the Nagi could possibly be the opposite of masataka or mitsuomi as taka means a hawk or falcon, which might refer to the Garuda. Also, it could mean that the Takayanagi's are the descendents of the Orochi (Eight Snakes). Also, Bob name could be really just be a pun or he could possibly have a much deeper, more meaningful role in the whole story than just being the strong, black guy. Let me know what you guys think.