Tensei shitara Hime Datta node Dansou Joshi Kiwamete Saikyou Mahoutsukai Mezasu wa.

Ikuto, a high school boy who loves shounen manga, is reincarnated in a magical world as a princess named Isabella. At first, Ikuto is happy because he always wished to be able to use magic. However, custom dictates, "The source of happiness for a woman is to devote herself to her husband" and "Women should not touch such barbaric things as magic." Not wanting to give up on her dream, Isabella uses the pseudonym Ikuto and disguises herself as a man. She then embarks on a journey with a handsome wizard to learn magic. (Source: Hakusensha, translated)