Akizuki-san wa Otona ni Narenai

The story centers on Yusa, a 25-year-old nursery school teacher. Yusa's boyfriend is Akizuki, a 32-year-old president of a toy company. Akizuki is handsome and capable, but he unfortunately still behaves in childish ways. When they begin living together, their everyday lives become more and more strange. Author's Twitter and Pixiv