Undercover cop Muscles enlists his childhood friends, the "Five Lucky Stars", to travel to Japan to help him catch a Yakuza group.
A corrupt Hong Kong cop flees to Tokyo to join his fellow mobsters, whose headquarters are secretly built under an amusement park (filmed in Fuji-Q Highland). Two loyal cops, Ricky and Muscle, travel there to apprehend him and uncover the mobsters’ lair, but Ricky is kidnapped in a fight. Muscle read moregoes into hiding and calls his supervisor to send help; since the mobsters already have information on the officers of the Hong Kong Royal Police Force, Muscle asks to send his orphanage friends, nicknamed the Five Lucky Stars, over. The supervisor agrees and collects the five friends, who are all either petty criminals or low-wage workers. They refuse to aid the police, but the supervisor cunningly sets up a false story in the media that accuses the five of robbing a bank of millions of dollars, blackmailing them into helping. They ultimately agree when the supervisor teams them up with a rookie policewoman, Swordflower, who becomes an object of lustful target to the five. They travel to Tokyo and that night, Kidstuff, who is the Stars' most rational and talented member, and Swordflower go to Muscle’s apartment. After defeating some thugs, Muscle reunites with Kidstuff. The operation is to send phony money to the mobsters to allow the five to enter their lair, and that way they can get closer to freeing Ricky and apprehending the criminals. After a prolonged battle at the bowels of the amusement park, the criminals lose and the Lucky Stars receive a place to live back at Hong Kong as their reward.
The fight scene between Swordflower and a Japanese gangster is one of the most memorable not just in this movie but in many Hong Kong action movies. Swordflower attempts to unlock the door to Ricky's cell not realising that a kimono-clad woman is slowly walking towards her. Ricky notices and alerts Swordflower to this. After opening the cell door, Ricky gets ready to confront the woman but Swordflower tells him to let her deal with the woman and Ricky goes to help the others.
The woman has a cold, emotionless look in her eyes and walks very slowly towards Swordflower, stopping a short while to step out of her slippers. As she walks towards Swordflower she starts slowly removing the belt of her kimono. Seeing this, Swordflower untucks her blouse, briefly showing a little of her stomach, and gets ready for action. Suddenly the woman charges towards Swordflower, slips behind her and starts choking Swordflower with the kimono belt and then throwing her to the ground. With the belt still wrapped around Swordflower's neck, the woman pulls Swordflower up with the belt, hits her face and flips Swordflower to the ground.
Swordflower gets up and the woman quickly whips off her kimono and holds it in front of her to cover her body. She drops the kimono to the ground and does a double bicep pose. The woman is dressed in black one piece suit and has extremely muscular arms with rock solid biceps. A look of shock is on Swordflower's face (eyes wide and mouth open) as she sees how muscular and strong her opponent looks. The woman turns her back to Sunflower and now she does a back double bicep pose, showing off not only her arms but also her muscular back. Swordflower realises she's in trouble but does not back down.
Both ladies charge towards each other and start exchanging blows. Both manage to block the other's blows in a flurry of shots. The woman kicks Swordflower who manages to block but the impact of the kick sends Swordflower back a few steps. The woman walks towards Swordflower and executes several kicks including a roundhouse kick. Swordflower manages to block all the kicks but her arms are hurting and she tries shaking the pain away.
The woman approaches and again starts attacking with kicks which are again blocked. Swordflower manages to step on the woman's foot, which temporary immobilises her, and she follows up with an upper cut followed by a hard forearm shot to the woman's stomach. The woman stumbles back, holding her stomach in pain. Swordflower has a defiant look on her face as though saying "I can defeat you". The woman recovers almost instantly and is back on the attack. She executes a high kick (which Swordflower blocks) but it turns out that kick was merely a distraction. As Swordflower blocked that high kick, the woman starts attacking Swordflower's legs. Four extremely hard kicks to Swordflower's left thigh causes her left leg to buckle. As Swordflower falls to one knee, the woman hits her with a hard punch that sends her to the ground.
The camera angle cuts to another scene and when it returns to this fight, the woman's head recoils as though she had just been hit in the face by Swordflower. Swordflower attempts to hit the woman again but she blocks it, pulls Swordflower's head backwards and hits Swordflower's stomach with a hard forearm smash. Swordflower screams in pain and the woman grabs Swordflower's hair with both hands. Swordflower tries to break the hold by smashing her forearms against the inside of the woman's forearms several times but the woman is just too strong and Swordflower is unable to break the hold. Therefore she also goes for the hair and both women are dragging each other to and fro by the hair.
Swordflower manages to fling the woman against the side of the wall which collapses since its only made of paper. However as the woman was grabbing Swordflower's hair, both of them went crashing through the wall. Kidstuff arrives on the scene to see both women still grabbing each other's hair. As she is much stronger, the woman manages to break Swordflower's hold by smashing her forearms against Swordflower's forearms. She follows this up with an extremely hard punch which sends Swordflower flying to the ground.
Kidstuff checks on Swordflower. Bleeding from the mouth and in obvious pain, she tells him that "she's really tough". Kidstuff approaches the lady who is in a defensive stance. She looks absolutely intimidating with her emotionless eyes and her chest, arms and forearms rippling with muscles. Kidstuff approaches the lady who is ready to attack however he hits her with a quick punch which knocks her out. A some what ridiculous ending however many would agree this is one of the best female fighting scenes in the Hong Kong film industry.