Thanks to some sneaky detective work inMy Hero Academia, the extent of Dr. Ujiko’s reach has recently been uncovered, and it is much broader than expected. Fans are well aware of Dr. Ujiko’s fascination with genetic mutations and has a certain God complex when it comes to Quirks, with the poor Oboro Shirakumo unfortunately falling victim to his experiments many years ago.
Considering that the mad scientist has access to so many institutions, other beloved innocents may have possibly fallen victim to Dr. Ujiko’s unsolicited interventions too. A certain member of the Todoroki family has spent a significant amount of time hospitalized and seems to be the perfect specimen with significant leverage potential.

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The Todoroki’s Troubles
Rei Todoroki dedicated her life to raising her children in a loving home, however, her husband, Enji (better known asthe No. 1 Hero, Endeavor), had entirely different aspirations. Although their relationship is rather strained, they still hold a spot in each others' hearts after everything that has happened; a fact of which Dr. Ujiko may be well aware. It is unclear if this mother of four’s hospitalization is a secret or not, however, a quick scan of patient records containing the Todoroki name would surely be an eye-catcher.
Endeavor did not choose to wed for love but opted to find the perfect Quirk to collaborate with, and Rei’s potent ice powers provided the ideal solution (in theory, that is.) The first three offspring had not acquired a balanced distribution of hot and cold powers, renderingthe kids ineffective in Endeavor’s eyes. All the blame fell onto Rei, and barely receded once the golden child, Shoto, was born, on the contrary, it is safe to say that their disagreements intensified. The No.2 Pro Hero (at the time) dreamed of raising his son with enough skills to surpass the great All Might and took the tough love approach as a teacher and father. Rei did all that she could to protect her kids from Endeavor’s harsh criticisms and disciplinary methods, only to receive the same treatment herself as a reward.

After years of constant abuse, something within Rei snapped and she could no longer stand the sight of her own brood, for their resemblanceto their horrid fatherwas too uncanny. At a particularly emotional junction in her life, Rei lost control and showered her youngest son with boiling water, before she even realized what she was actually doing. She was subsequently booked into a psychiatric ward, for her own safety and the sake of others, and has remained at Fujitani Hospital to this day.
The Not-So-Good Doctor
While Rei refrains from using her superpowers to fulfill a Hero’s role, it is safe to say that herQuirk is much more powerfulthan first impressions dictate; they managed to attract the attention of the fastidious Endeavor. He deemed Rei’s Quirk worthy enough to adequately compliment his own raging inferno, and, when looking at how Shoto’s skills have turned out so far, he clearly made no miscalculations there. For a man who shows such a keen interest in collecting Quirks, how could Dr. Ujiko ever pass up the opportunity of sampling this specimen if Rei is indeed within his reach?
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The exact medical institutions that Dr. Ujiko has an influence over remains uncertain, as Hawks' main priority was to pinpoint the villainous doctor’s precise location to Jaku Hospital, subsequently pushing Fujitani Hospital out of the investigation. It is important to note that when the police forces are debriefing thePro Heroes about their mission in Season 6 episode 1, they ensure to mention that Dr. Ujiko’s corruption has taken hold of orphanages and nursing homes too. Coincidentally, Fujitani Hospital happens to fall into that very same assisted-living category, too. The ambitious doctor has tried to cover all the bases by partnering up with private clinics and hospitals as well, suggesting that nobody is truly safe from Ujiko’s hold.
Speculations and Conjectures
It is probably safe to say that Dr. Ujiko did not build up his extensive collection of Quirk samples based on voluntary donations alone.All For One can steal superpowersfrom cadavers but it is unclear if the mad scientist has figured out a way to do the same, or if he has to rely on producing Nomus to obtain the desired result. It is evident that Dr. Ujiko not only uses his skills to reanimate corpses but can also add certain Quirks to the living, such as in Shigaraki’s case. He could therefore perform similar feats on some of his unsuspecting patients, augmenting their DNA with supplemental powers, to add villainous members to his army, or merely for the sake of experimentation.
Adding Rei’s potent ice powers to his stockpile would certainly be a worthwhile accomplishment for this proud man. Sure, it may take several weeks for the Quirk and the host to meld into one; but as far as viewers are aware, Shoto and his family did not keep up with regular visits for Rei’s entire hospitalization, and she could have therefore been experimented on without anyone knowing. Healready has Dabi to play with, so why not add more Todoroki’s to the mix? As Hitoshi has already proven, brainwashing is entirely possible inMy Hero Academiaand, if Dr. Ujiko found a way to produce the same effects, he could create his own little secret spy himself.

The Todoroki family is beginning to grow excited at the thought of Rei’s return home (which is scheduled any day now) and would never think to suspect any nefarious intentions from their “healed” mother. She could, however, be a ticking time bomb, obliviously waiting for the signal to turn into a Hero-killing machine at the most opportune time, and will likely have no idea about her alterations so as to adequately keep up the rouse. Dr. Ujiko could then essentially take out the current No. 1 Hero and one of themost powerful students in UA High Schoolin one go. If All Might’s defeat caused chaos within the community, imagine the upheaval such a horrific affair could produce.