Mako Takanashi, younger sister to unethical university lecturer Shuichiro Takanashi, presents herself as a reserved high school student skilled in martial arts, concealing a merciless nature that mirrors her brother’s. Bound by a warped loyalty cultivated through Shuichiro’s manipulation, she becomes a pawn in his experiments. He embeds the "stone of life" within her, granting immortality, heightened strength, and regenerative abilities exceeding those of Euphrosyne Studion. This power intensifies her brutality, driving her to savage confrontations.

During a clash with Euphrosyne, Mako combines strategic cunning with arrogance, exploiting her enhancements to dominate the fight. Overconfidence proves her downfall: a collapsing church bell severs her body. Still, she persists, attacking relentlessly until Euphrosyne destroys her skull to reclaim the stone.

Mako’s ruthlessness surfaces earlier when she impales hostage Sayaka Kamoshida with glass to resolve an inconvenience. Later, she betrays Shuichiro in a perverse display of devotion, tearing out his heart and sealing his fate. Her arc ends in annihilation, a tragic antagonist shaped by familial manipulation, unchecked power, and latent volatility.