Seibetsu Bug ga Hassei shimashita!? Gender x Bug

Synopsis

Haruki Sakuma is a high school freshman boy who loves games. He is a coward who often tries to please those around him and has a hard time saying no, always relying on Karen Minatsuki, who goes to the same school. One day, a loud thunderclap rings through the school, and before he knows it, Sakuma has turned into a girl! When he wakes up, he finds himself in the world of his favorite game, "Mirage Universe," and due to a game bug, Sakuma and Minatsuki have switched genders!? (Source: Shogakukan, translated)