Matsuri Oyama

Matsuri Oyama is the mother of Mahiro and Mihari Oyama. She has spent the past few years working overseas, which initially made it seem like she was unaware of Mihari's experiment on Mahiro. However, it is revealed that Mihari had been keeping her informed from the beginning. When Matsuri returned home for a visit, she wholeheartedly accepted Mahiro's transformation, as the experiment had helped Mahiro become more active and engaged with life again after a long period of isolation. (Source: Onii-chan wa Oshimai! Wiki)