You can do other things usually like take them out with a ninja star, poison them, blow gun etc. You can get into direct fight with enemy but usually you don't want to.
Tenchu has always put great important in stealth and stealth kills. For example in Tenchu Wrath of Heaven, every stealth kill you got filled up a kanji character (basically a meter)you had on the screen and once it was filled your character would learn a new ability. Previous installments certainly were not fast-paced games.
That is one of the reasons why I actually enjoy the tenchu series, since I've always pictured NInjas as stealth assassins and thats exactly what you are trying to do here. Watch an enemies pattern, figure out when the best time would be to take them out without letting others know. Sometimes its easy, sometimes its pretty hard.
