Ryo Ninomiya is Takeru's best friend and is something of a ladies' man, and is consistently called "Ro-baby" by Sakurako and Amika. He finds Akari sitting alone by a lake, and later gains some sort of power over the elements similar to how Takeru gained his powers shortly after meeting Hikari. He found Akari and takes her in as one of his family members. Ryo does have feelings for Akari, but Kimi keeps the two from having any sort of relationship.
Ioneos is like Kuon's "older brother," as he and Kuon are created from the same type of magical crystal. However, Ioneos' appearance and size are much larger and sleeker than Kuon's because he is comprised of an entire crystal, save a small chipped fragment which Kuon is made from. He was sealed inside of one of the school's stone pillars until Hikari accidentally released him during a routine fire drill. The entire school was subsequently demolished after the blast following Ioneos' release. Jennifer nicknamed him "Oniita," saying that his original name was too long. In the end, Ioneos turns into mud along with Kuon and become crystals. Kuon being the little chip and Ioneos being the big crystal. Jennifer puts them on a necklace and wears the crystal. from wikipedia
Jennifer Portman is a crazy American super-scientist who came to Japan to study the "Extended Definition", a species' ability to prevent its own extinction, which usually manifests itself in said species transforming into a monstrous form that maximizes its combat potential, and gives it the instinct to attack or kill Hikari. She moves in with Takeru, Hikari, and Mari. She's rarely to be seen without some kind of alcohol and is somewhat of an exhibitionist. Although out of work she appears ditzy and idiotic, she is extremely intelligent at her work. from wikipedia
Hikari is a girl whom Takeru finds in the forest and falls in love with in the first episode. Hikari also likes Takeru ever since they met as well.She is very cheerful and thinks that almost everything she sees is wonderful or incredible. However, not much is known about her. At some points during the series she has moments that a voice talks and makes everything sound depressing.
Takeru Takemoto is this series' main character. He comes off as a lazy and unmotivated teenager, but is really just unsure of his place in the world. He was the one to find and name Hikari in the first episode. He can transform into a powerful being with superstrength and sharp appendages. He has an apparent love interest in Hikari, blushing and getting flustered when near her, and eventually admits he likes her.
These two girls love Ryo, or "Ryo-sama". They made Hikari's and Akari's clothing. They also egg on the love triangle between Takeru, Mari and Hikari. They seem to have some sort of relationship with each other--accented by the fact that they nearly kissed in one episode--but their love for Ryo seems to prevail over it all. from wikipedia