Mahiro Oyama is a central character in the anime series 'Onii-chan wa Oshimai!'. Originally a shut-in NEET, Mahiro's life takes a drastic turn when his sister, Mihari, experiments on him, turning him into a girl. This unexpected transformation thrusts Mahiro into a new world full of challenges and personal growth. Despite the initial shock, Mahiro gradually learns to adapt and embrace his new life, developing stronger bonds with his sister and making new friends. His journey explores themes of identity, family, and personal change, making him a relatable and engaging character.