Maeda Keiji is the adopted nephew of Maeda Toshiie and his wife Matsu, and he is a free-spirited wanderer who refuses to be tied down by the responsibilities of his clan. His past holds a deep and painful connection to the brutal conqueror Toyotomi Hideyoshi. He was once a close friend of Hideyoshi, but their bond was shattered when Hideyoshi's lust for power led him to murder Nene, a woman Keiji loved. This traumatic event drives much of his internal conflict, as he struggles to reconcile the memory of his former friend with the monster he became.

Keiji is widely known as a happy-go-lucky man who loves festivals, dancing for the sheer joy of it, and playing lighthearted pranks on his uncle Toshiie. He believes strongly in the power of love, often claiming it makes people stronger, and he has a great fondness for sake. He is frequently accompanied by a small, mischievous monkey named Yumekichi. While he genuinely cares for his adoptive family, he sometimes shows resentment toward them because they object to his carefree and unconventional lifestyle. Despite his jovial exterior, underneath this facade lies a more troubled soul. The death of his friend Hideyoshi weighs heavily on him, and he often uses his philosophy of love, peace, and diplomacy as an excuse to run away from confronting his own problems and painful memories.

In the story, Keiji initially defies his uncle and aunt's attempts to bring him back home, choosing instead to travel the country. After Hideyoshi's death, he aligns himself with the Uesugi army, fighting alongside his close friend, the warlord Kenshin Uesugi. During his travels, he meets the skilled mercenary Saika Magoichi and falls hopelessly in love with her at first sight, dedicating much of his journey to following and trying to protect her, much to her annoyance. His path can lead him to return to the Uesugi, rejoin the Maeda clan, or set off with Magoichi and her Saika mercenaries. Over time, his character develops from a simple vagabond into a leader, eventually taking on his uncle Toshiie's position as the head of the Kaga clan and commander of the Maeda Army. While still free-spirited at heart, he gains a sense of awareness and responsibility for his role, and he actively opposes the turbulent era brought about by others. His journey ultimately forces him to confront his past with Hideyoshi, coming to a painful but final understanding that they can never return to their former friendship.

In battle, Keiji wields a ludicrously oversized nodachi, a type of Japanese greatsword, which he is strong enough to use with one hand. He has a unique fighting style that includes throwing his sword's sheath into the sky and catching it when he needs it. His combat abilities are characterized by a special technique that allows him to cancel his own attack animations into new ones, enabling him to perform seemingly endless and confusing combo attacks. Furthermore, he possesses a remarkable ability to cheat death itself once per battle, simply standing back up as if he were joking after a fatal blow. His deep-seated belief in the power of love and his free-wheeling, festival-loving nature define him as a truly unique and unconventional samurai.