Ruu

Ruu is an alien baby from the planet Otto that got sucked in a dimensional chasm and accidentally ended up in the planet Earth together with his sitter-pet Wannya. Upon arriving in the Saionji temple, he met Miyu and Kanata and thought of them as his parents; calling them "Mama" and "Papa".

Appearance
Ruu has a blonde hair and violet eyes. As described by Aya, his eyebrows resembles Kanata and mostly resembles Miyu.

Ability
All babies from planet Otto have psychic powers as mentioned by Wannya. Ruu has an ability to fly and float things, as well as psychic powers where he controls objects at his own will without touching it. He was able to feel presence of different aliens as well as being bad or good.

Plot
Ruu safely arrived in the Saionji Temple through his mini UFO spaceship and was taken care of by Miyu and Kanata. After feeding him, he started calling them "Mama" and "Papa".

Anime and Manga Differences
There are several events happened in the manga that did not occur in the anime.
 * At the last chapter of the manga, Ruu bumped into a teenager Miu, Kanata and Miyu's daughter when he returned to planet Earth. While in the anime, Ruu returned to planet Earth all grown up and visited the Saionji Temple seeing Kanata and Miyu with their baby daughter Miu.