Kōshi Mizuchi

is the a former Clansman of the Gold Clan, having worked as a doctor with the enhanced ability of regeneration.

Appearance
Kōshi is an aging man with slicked back, gray hair and colorless eyes; he lacks the normal irises and pupils in his eyes.

Personality
Kōshi is an ambitious, manipulative, brutal, intelligent and ultimately cruel man who goes to great lengths to meet his own goals. Due to the contents of SIDE RED, it can be inferred that neither the age, sex, or background of a person will stop him from doing whatever he has to do in order to achieve something.

He's also a very curious man, fascinated by the concept of a person going further than what is already thought to be their limit, a trait developed thanks to this discontent with realizing that the Gold King's power has already pushed him to his own limit with his talent.

History
A Clansman of the Gold King, Kōshi was left discontent with the realization that his abilities were at their limit, and he could do nothing better than regenerating himself and others. However, he later began conducting brutal experiments on dangerous Strains, unbeknownst to the Gold King himself, and is said to have 'destroyed their bodies', only to reconstruct and brainwash them, essentially. Three named Strains with this fate are 'Grasshopper', 'Pyrotechnic', and 'Senkouki'.

He also attempts to use Anna in his attempts to make a Strain a King, specifically the new Blue King. Thus, he burns, drowns, and chokes Anna to 'stimulate her power' and make her connect to the Slate. Every time this fails, he'll soon go back to torturing Anna or threatening to harm Honami Kushina (Anna Kushina's aunt).

In the end, however, Mizuchi wastes his energy trying to repeatedly heal a badly burnt 'Senkouki', as the Strain fights Mikoto. Soon, 'Senkouki' is burnt from the inside out, and now a livid Kōshi keeps yelling at Anna to come back to him, only to have his arm burnt in the process, and thrown to the floor unconscious when Rabbits apprehend him.

Powers & Abilities
Gold Aura: As a member of the Gold Clan, Kōshi possessed the gold aura.

Regeneration: Kōshi's 'talent' was based on his career as a doctor that he gained enhanced healing abilities and regeneration, in which these abilities affect both himself and others.

Etymology

 * The name Kōshi means "tall, high" (高) (kō) and "will, purpose" (志) (shi).
 * Kōshi's surname Mizuchi means "honorable" (御) (mi) and "hammer" (槌) (tsuchi/zuchi).