In a magical part of the galaxy, the prince of the Tambourine star world has been betrothed to marry one of two princesses; but Comet, the princess of the Harmonica star world, couldn't care less. Thus, much to her dismay, when the prince flees to Earth to escape his fate, Comet is sent to find him and return. Now, with the power of the stars and a magical locket, Comet sets out on an adventure to find the prince, have fun, and experience the life of an earthling first hand!
One day in the lab, Professor Utonium, his son Ken and the digital pet Peach accidentally discovered the recipe for the powerful Chemical Z - after which large glaciers started to appear in the city! After firing the chemical into the glaciers, beams of white light fell from the sky onto three unsuspecting high school girls; and thus, the Powerpuff Girls Z were born! Now, the boy-crazy Momoko, popular Miyako and tomboyish Kaoru must protect Tokyo City from the evil monkey Mojo and other villains, while trying to live "normal" high school lives!
Cosmic Girl and Powerpuff Girls Z are both magical girl shoujo titles that will appeal to the same audience (young girls). PGZ is admittedly a lot more action-packed and high octane (if you can call it that), while Comet-san has more cuteness. Fans of one may enjoy the other.
One clear festive evening, Lucia, a mermaid princess, rescues a young boy from drowning. With him, she leaves the source of her beautiful singing voice: a pink pearl necklace. Several years later, Lucia has grown into a young woman, and embarks on a quest to the human world to reclaim her pearl and find her lost love.
Comet-san and Mermaid Melody are both shoujo titles with cute characters and a whole lot of fun. I personally liked Comet-san better, but if you liked the magical girl elements of one, you'd surely like the other.
Eighteen years ago, the Platinum Tiara, which gives its wearer magical powers, was reassembled. At the same time, five "Princesses" were born, to the worlds of Earth, Heaven, Celestrial, Fairy, and Hell. These five princesses quit maturing at the age of 10, and are all competing to become THE Platinum Princess so they can grow up. This story is centered on Yuuchi, from the kingdom of Earth.
Both main characters are "troublesome" girls who are meant for greatness. While Yucie is in a competition to become Platinum Princess and falls in love with the Prince, Comet-chan must find the Prince she may marry while not particualarly caring (at first anyway).
Sakura Nina, a magic girl from the Magic Kingdom, comes to the human world to continue her training. It would have been a simple scenario, if not for the fact that Nina's magic skills are subpar at best. Nina and her best friend Ayu subsequently find themselves turning normal high school life into crazy adventures, day after day, with a magical twist. But as time goes on, there are questions that must be answered -- why is Nina really in the human world? And why is her childhood friend, a black magic user named Maya, in the human world as well?
Ultra Maniac and Cosmic Baton Girl are somewhat similar. Both of the main characters are candidates for marrying a prince, are sent to Earth for a task, and have magical powers. If you like what went on in Cosmic Baton Girl you would also like Ultra Maniac (or vice versa).