Welcome to the quirky and hilarious world of Oniichan wa Oshimai! where Mahiro Oyamas life takes an unexpected turn when he wakes up one morning as a woman. It turns out that his crazy scientist little sister, Mihari, has conducted an experiment on him with disastrous results. Determined to find a solution, Mahiro must navigate through this bizarre new reality while trying to return to his normal life of gaming. Get ready for a wild ride full of comedy and chaos as Mahiros life is forever changed in ways he never could have imagined!