Danshi Koukousei Wa Isekai De Jk Ni Natta summary:

A serious and uptight male high school student becomes a girl in another world...!? Cattleya Lanoquid is a girl from another world who longs for magic. On her 16th birthday, her mother tells her that the way to save their household finances is to... get excited...!? However, Cattleya was actually Ranka Harumigawa, a neat and serious male high school student in his past life!! Ranka (Cattleya) wants to become a respectable adult, but is torn between that desire and his hidden desires...!!