Yakuza is one of the hardest bosses in the game, so get ready for a tough fight! The fight begins with a salvo of three fireballs from off-screen. Stay as close as possible to the left or right wall. When the flames die down and Yakuza starts to crawl around the screen, roll into the Morph Ball and hug the corners; this will make it impossible for the Yakuza to grab you. When it is finished, the Yakuza will open its mouth to spit out more fireballs. Fire Super Missiles rapidly into this weak point. If the Yakuza grabs Samus, quickly tap Left, Right, A, B to escape; otherwise, she will take massive damage from the creature chewing on her and a the body blow when it drops.
Another good trick for the beginning of the battle is to stand between two of the fireballs and jump into the air. Yakuza’s mouth will remain open while it hovers in the air, and you can hit it with several Super Missiles before it attacks again!
Once the Yakuza has taken enough damage, its legs and abdomen will explode, leaving just a head. The head will jump in mid-air using the Space Jump power, and it will periodically spit out small maggots. At this point, stay in the corner and aim diagonally up. Fire Super Missiles at the head when it opens its mouth at the top of its jump. You can fire a steady stream of Super Missiles to destroy the maggots that drop, but you can also use the Charge Beam to conserve ammunition.