Maken X is a sword - a "Soul Sword" that possesses a unique ability called brainjacking. It can take over the mind and the body of another creature and adapt all its strength and weaknesses. Maken X is also the hero of the game - a wandering mutant spirit of the sword. The ability to manipulate a person's "psi", or soul, was discovered in a research lab. The chief scientist is kidnapped by terrorists and his daughter Kay awakens Maken X who now must assist her on her dangerous mission.

In contrast to the previous games in the series, Maken X is a first-person action game with emphasis on melee combat, that offers the player the possibility of controlling minds and bodies of thirteen characters the player may meet while journeying. Each character has their own attacks, advantages, and disadvantages. Throughout the game the player has to make decisions that will influence the plot and bring the game to one of its seven endings.