You begin Stage 1 on top of a fence in a city. Ninjas will begin attacking you immediately, so when you're safe, start moving to the right (the end of every stage is to the right).
When you get to the semi-truck, depending on what version you are playing the door on the side might open. If so, several blue ninjas will pop out in waves to attack you.
Look for two ninjas dressed in red. They will respectively drop a time bonus, and a cola.
Near the end of the stage you'll fight two Blue Sword Ninjas, which you need to kill before the boss arrives.
Boss: Karnov
Karnov is an easy boss, and you'll see him several times throughout the game. He has two abilities: jump, and breath fire. His jump is very random, and sometimes you will never see it. If he does jump, all he will do is hop over your head and try and attack from the other side. You don't have to move when he jumps, because his movement path is high. If you are close to him, he will attempt to breath fire. If you are standing when he begins the attack, he will shoot high. If you are ducking, he will kneel.
To fight him easily, walk up to him and punch him in the stomach. When he starts to belch, duck and start attacking. If done right, he will then kneel, take a hit, then allow you to retreat before he shoots fire low. Remember to either retreat slightly or jump to the upper/lower floor. When he stands up or jumps after you, walk up and repeat the attack sequence. This takes 20 hits to defeat with your bare hands.