Commonly known as Zero. Male personality. Possesses a human form appearing to be in his mid-20s. The first Mecha Ninja created by Dr. Momochi. He has an archaic personality and way of speaking. He views Guest as his lord and master, addressing them as "My Lord" or "Guest-dono." His absolute mission is to destroy the Koku Clan. Abilities: Stealth using optical camouflage, clone techniques using hologram projection, and numerous weapons hidden throughout his body. His primary weapons are two katanas, Nichirin and Gekko. His ultimate move is the "Zero Infinite Slash," which uses super-acceleration to mince enemies in an instant.

Commonly known as Sakura. Female personality. Her human form appears to be in her early 20s. The second Mecha Ninja created by Dr. Momochi. She calls Zero "Big Brother." Compared to Zero, she is more modern and casual in her speech, often getting scolded by Zero for addressing Guest without honorifics. She has a strong sense of justice and a fierce fighting spirit against the Koku Clan. Abilities: While her combat prowess is high, she excels in hacking and disrupting electronic equipment. Her ultimate move is the "Cherry Blossom Flame Blizzard," which envelops enemies in a flurry of flaming petals.

The third Mecha Ninja created by Dr. Momochi. Male personality. Dr. Momochi failed to let him escape, and he became a vanguard for the Koku Clan. He scoffs at Zero and Sakura's sense of justice as nothing more than programmed routines. He follows the Koku Clan in search of stronger enemies, finding his purpose in life through combat. Unlike Zero and Sakura, he does not have a human form. Abilities: The strongest of the three in a head-on fight. Possesses incredible strength and armor that ignores heavy weaponry, along with speed rivaling Zero's. He uses a massive kanabo (metal club) as a weapon and can transform into a monstrous form called "War Demon Mode."

A classmate of Guest. Female. An honor student with glasses and long hair. A member of the art club who has won numerous awards in competitions. She is kind to everyone and watches over Guest with a smile. Her true identity is a member of the Koku Clan. She has been secretly monitoring Guest, the grandson of Dr. Momochi. Guest and the Mecha Ninjas are unaware of her true nature. While loyal to her mission, she secretly longs for a normal life. Abilities: Ninja Art: Super Beast Scroll. She can materialize and freely control animals drawn in her sketches. Even if defeated, the animals can be revived as long as the sketch exists. Furthermore, these animals are based on Shiori's imagination and are stronger and more ferocious than real ones.