Nana Astar Deviluke/Plot

Nana made a debut together with Momo in chapter 97 of the To LOVE-Ru manga. They were responsible for the Trouble Quest, a virtual video game they built to observe the true character of Lala's friends and especially her loved Rito. After recognizing that Lala had good friends, the twins returned to planet Deviluke.

A few chapters later, in chapter 108, the twins went back to Earth escaping from Deviluke and their study, as Zastin is instructed by Gid to bring the twins back home. They tried to escape, but when Nana and Momo started fighting each other, Zastin, Maul and Smutts were able to catch up to them, and a battle ensued. It was revealed that Nana and Momo also have D-Dials, which summon animals and plants, respectively. Finally, they defeated Zastin and his henchmen, and they convinced their father that they're going to stay on Earth with Lala.

During Nana and Momo stay in the Yuuki household, they created their own room in the attic using the technology of space distortion. They also took care of all their necessities to avoid bothering Mikan for cooking, cleaning, etc. However, they still came down sometimes to eat Mikan's cuisine.

Throughout the series, Nana unconsciously develops affectionate feelings for Rito. She thinks of him as a shameless pervert, and is widely known for calling him a "beast". After she talked with Haruna in chapter 117 and found about her feeling for Rito, Nana learned he can be kind sometimes and is often grateful when he puts her needs before himself. She begins to have feelings for him when he saved her from falling.

In To LOVE-Ru Darkness (manga), Nana, along with her sister, become Sainan High's students, she makes friends with a girl named Mea and she gets shocked whenever Mea admits something perverted to Rito. Eventually, the friendship between Mea and Nana becomes very strong; however, Mea turns into her semi-weapon form and tells Nana that their friendship was not real! Nana was petrified and traumatized after she saw Mea's true form and personality.

Rito tried to console Nana. When that didn't technically work, Rito embraced Nana. With that hug alone, plus some encouraging words about friendship, Nana finally realized what she had to do. She had to approach Mea and "opened her heart". Obviously, Mea used her semi-weapon abilities to scare off Nana again; however, Nana has shown a huge amount of courage and she faced the heartless semi-weapon. Nana stood there boldly and she confessed her care for Mea. This somehow opened Mea up. Finally, Mea understood what a friend truly was. This part of the story has shown Nana's bold bravery against something quite deadly, and this has shown Nana starts to open up to Rito. In fact, she even tried to sleep in Rito's bed afterwards (although inadvertently halted by the presence of Momo).