Spoiler alert: The following section contains plot-specific details.(Skip Section)
Now, to finally defeat Kirby, the old rivals have become partners, taking on Kirby as a battle team! And so they sent Kirby a challenge. They lay in wait on the Summit of a lofty tower reaching to the heavens, known as the Buddy Fighters Tower.”
The Buddy Fighters Tower is a massive tower constructed on Planet Popstar. It is described in-game as "reaching to the heavens." It has a medieval architectural design, with distinct brown brickwork. The tower extends into the clouds above; the visible part has four balconies, each crenellated. Hanging from the exterior are shields adorned with King Dedede's and Meta Knight's insignias. A shallow staircase leads to the front doorway, which is marked by yellow, pink, and blue star images. The tower is surrounded by a crescent-shaped, crenellated outer wall. Reliefs of Masked Dedede's mask protrude from this wall.
The Buddy Fighters Tower is a central focus of the game's Story Mode, The Destined Rivals. King Dedede and Meta Knight team up to defeat Kirby. They send a letter challenging him to a team battle; though Kirby cannot understand the letter due to his illiteracy, he accepts their challenge. The duo waits at the peak of the tower, with each floor below offering a different duel against other foes.
Kirby and his buddy expects to find the team, but face Twin Woods instead. Another encounter with King Dedede and Meta Knight is discovered to be a hoax, as two Waddle Dee imposters took their forms. When the villains are actually fought, they retreat after their defeat. They muster all their strength and teamwork to face Kirby and his buddy once more, and suffer a demoralizing defeat.
Kirby and his buddy are ready to nap after this victory. The sky darkens, and amid lightning storms the Buddy Fighters Tower rises to the point of "piercing the heavens." The two sense an ominous aura and climbs the tower, only to battle Dedede and Meta Knight once again at the Summit. When defeated, Meta Knight's mask breaks and Dedede tosses him a dark replacement. Dedede uses the Mask of Dark Bonds to reinvigorate them, but Kirby and his buddy devastates them with the Buddy Star Blaster. The mask's power is nullified as the king and knight launch into the distance.
The Buddy Fighters Tower is used as a framing device to accompany The Destined Rivals's structure; Kirby fights a sequence of battles against various Kirbys, Bandana Waddle Dees, Gooeys, and/or Magolors, culminating in a boss battle at the tower's Summit. The player can bookmark battles to return to later, as well as retry battles. Between each fight, the player visits the Item Room where three randomly-selected Story Items are presented. He/she must choose one to keep for the remainder of the campaign. These include Stones that upgrade health and strength stats, Charms that decrease damage taken from certain hazards, Badges that allow the player to deal more damage to certain foes, and more.
The length of the campaign varies by chapter. Despite the tower's consistent height in the loading screen diagram, the Summit in Chapter 1 can be reached after climbing only four floors. The true Summit is the 50th floor in Chapter 5, where the atmosphere is thin and the stars glisten overhead. The length of each chapter is as follows:
Bosses appear after several floors, and one is always present at the Summit. These bosses include Twin Woods, DuoEdge, Shadow Kirby, and variations of King Dedede & Meta Knight. The latter are always fought on an arena that is built into the Buddy Fighters Tower, called the Stage of Destined Rivals or Stage of the Partners. This area is circular with a checkered stone floor. Six pillars decorated with Dedede's and Meta Knight's emblems support an overhead dome, and reliefs of Masked Dedede's mask serve as torches. Statues of the team proudly brandishing their weapons are erected in Chapters 4 and 5, and the ceiling is removed in the latter chapter.
At last, it was time to battle King Dedede and Meta Knight! Or so Kirby thought. To his surprise, it was Twin Woods waiting at the top! After defeating Twin Woods, Kirby and his buddy seemed to reach a dead end. Luckily, the defeated Twin Woods dropped a door key leading higher into the tower. Kirby and his buddy once again begin to climb, setting their sights on the Summit where King Dedede and Meta Knight await!”
After a tough fight, the victorious pair was ready to settle down for a nice little snooze. But suddenly the Buddy Fighters Tower grew to such a height that it seemed to pierce the heavens! They sensed the presence of the king and knight far above the clouds, radiating their sinister power unlike anything they had felt up to now. Kirby and his buddy set out once again to climb the heaven-piercing tower, which now has hints of something sinister... This will truly be the final showdown!”
— The Destined Rivals, Chapter 4 • Kirby Fighters 2
A stillness fell over the Summit of that tower which pierced the heavens. The stars of the night sky were so close that they were within arm's reach. They seemed to celebrate the partners' victory as they went on sparkling, forever and ever...”
— The Destined Rivals, Chapter 5 • Kirby Fighters 2
A soaring tower has appeared! Here, you must start from Floor 1 if you get a game over! Can you master this true challenge?”
— Announcement • Kirby Fighters 2
Most stages are set outdoors, often taking place in nature or in a cosmiclocation. There is no explanation for why or how these environments are housed on each floor of the Buddy Fighters Tower.
Story text in Chapters 1-3 states that Kirby acquires a key to progress further in the tower. The keys are not shown on-screen nor can the player interact with them.