
does this have a novel, or is it just manga? cuz i would love to read the LN, (if it exists)

It have novel series.

3 books and 2 side stories.. So 5 in total. There are extras that came out with first addition and some need to send the stamps from the book in order to get them. Also there are 2 drama CDs of the novel book1. 2 volumes of manga ended at around 70 percent of the novel book 1, so you can expect 8-9 volumes of manga which release 1 volume a year.. > <

You can Dl first 3 volumes here
http://www.yaoiotaku.com/forums/threads/46719-5-nin-no-ou-1-3-By-Eniwa-JP
There are also manga volume1 and 2 and also drama cds that you can DL from yaoi otaku. http://www.yaoiotaku.com/forums/threads/46719-5-nin-no-ou-1-3-By-Eniwa-JP
SPOILER ¡!!!!!!!!!!
No, he did not grow up. This series is not some master slave or anything like that. There aren't many sex scenes. In the very beginning blue king will only sleep with Seiji only too keep his symbol on him.
Suyou the cutest bunny ever ლ(´ڡ`ლ)
Its missing a prologue that explains a little bit about Muya and Suyou relationship until he gets sealed. it should have been the chapter 0