Rando Musashi is a tough guy, an obnoxious karate star, the school troublemaker and... the most popular girl in school?! Rando was riding the bus home one day when a sudden crash resulted in a horrible wreck. He was immediately taken to intensive care under plastic surgeon extraordinaire Dr. Manabe, who treated Rando's maimed face. Yet unfortunately Dr. Manabe mistook a picture of Rando's school crush for a picture of how Rando looked before the accident. Rando awakens from a coma a full year later to find that he now has the face of Rina Kurimi, much to his dismay! He rushes out of the clinic in terror, only to run into Rina herself, who mistakes Rando for her twin sister that ran away years ago. Now living at Rina's house, Rando is now forced to play the part of Yuna Kurimi while at the same time searching for the real Yuna and attending school. Even with the help of Dr. Manabe, Rando has his work cut out for him!
Both mangas are about a male protagonist, who had a life threatening accident, but his life was saved due to unusal work of some perverted scientist. And thx to that he now have to live as a girl, and stay around the girl he has a crush on. The only real difference is that in Pretty Face the main hero only have female face, and the rest of the body is male, while in Ichinensei ni Nacchattarahe is not only fully turned into a woman, but also into a child.
Both are Shounen/Ecchi/Gender-Bender/Comedy mangas, if you enjoy one you should enjoy the other as well.