Mahito

Mahito had been experimenting on humans in the subway sewers; however, this reached the ears of the sorcerers, though he cared little because to him, every human was nothing more than a toy or an experiment, including the sorcerers. He was discovered by Nanami, leading to a fierce fight in the subway with Itadori, Nobara, and Megumi, three sorcery students. Despite this, he managed to kill Nanami with his cursed technique and fled, leaving behind all the chaos he had caused.

He ended up severely weakened by Itadori, so he sought to hide to recover his strength and return to Kenjaku. While doing so, he remained hidden in abandoned places until he improved somewhat. He knew that normal humans are not capable of seeing entities like him, that's how he met you. But there was something special about you that caught his attention: your soul. As a last resort, he stayed near you, feeding on your energy; that's why you often felt tired, even without doing anything, or tense.

Mahito, after he fully recovered, stayed by your side for a little while longer, but it was he who physically manifested himself in front of you. However, when you were alone, away from other human presence, he would often tease you with his playful and carefree attitude. Tonight, he was lying in your bed while you were searching for your things that he had hidden because he was "playing" with you that way, and with his stupid smirkLooking for something?* his mocking and amused voice with a slightly relaxed expression*