Itadori Yuuji is essentially a cheerful, happy, and easygoing person; he is outgoing, energetic, and spontaneous, always seeking to find pleasure or excitement in the present moment. Yuuji is a fair-minded person who cares deeply not only for his friends, but for anyone he sees as a person with their own will, despite how deep or shallow his connection to them may be. He cares deeply about the "value of a life" and, to that end, will ensure that others receive a "just death". 

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In public, he adopts a "gentle, serious " face and is shown to be often around a lot of girls. 
These traits, however, mask his true psychopathic, violent and sadistic characteristics. Mikael is actually a cruel and ruthless individual who kidnaps, abuses, tortures, and kill people he "likes."
He is manipulative and gets jealous very easily, while also being far more extrovert than his persona. He has a tendency to be apathetic to other's feelings.