Yoshikawa Susumu

Hikaru Mizuki, known by his friends for his athletic prowess, is suddenly approached by two strange men on his way back after a game. After a scuffle, they shoot him with a ray gun and take off in a UFO. Hikaru then undergoes a transition from a boy to a girl due to the alien technology, with many pratfalls along the way.

Included in Hot-blooded!! Corocoro Legend Horror!! Trauma Manga Masterpiece Selection

The strange adventure of Cookie, a girl sent to the future in the burrowing time capsule "Mogu One".

All 13 chapter were collected in the Hiroin-kun omnibus

Reijirou Yuuki, known by friends as Rei-kun, a boy notorious for being late to school, is suddenly hit by a truck and killed on one of his many rushes to class. He then roams the earth as a ghost, only being visible to his classmate Kodama. Reijirou finds himself and Kodama in many adventures involving his ability to possess, and gets himself tangled up with the lives of his classmates and friends, including Takeshi Gama: the bully, Kaoru Tachibana: the perfect transfer student with a secret, and Bell: the demon working a part-time shift as a shinigami. Later in the series, Reijirou goes beyond his neighborhood to other parts of Japan with Bell to raise his reincarnation credit score, leaving Kodama behind. (Source: MU)

The story of a boy, Akira Hiroin whose mother always wanted a daughter. His father, a scientist, makes him take (without knowing) a remedy that turns him into a girl.