One year ago, an alien spacecraft crashed into Tokyo Bay, leaving the crew stranded on Earth. The aliens are granted Japanese citizenship and begin a home-stay program to learn about human culture. When one DearS goes astray and wanders into the life of a high school student named Takeya, the adventure begins and this DearS is about to learn things they don't teach you in school!

Aliens called "DearS" have landed on Earth and are now a normal part of society. In order for the "DearS" to learn Earth's customs, they are sent to random high schools to "home-stay." When Takeya helps a DearS in his school, she calls him "Master." Thus begins the humorous life of Takeya and his sexy alien follower, Ren, who tries to figure out the wacky customs of this place called Earth!

Can life be any better for Takeya? He's surrounded by three beautiful women: Ren, Myu and Neneko. Unfortunately, some things can be too good to last when a DearS agent arrives to take Ren away as a defective slave. She will have to learn free will if she truly wishes to demonstrate to the rest of the DearS community that she really wants to stay with her new master.

Meet Nia. Her trainer Xaki is teaching her to be a Biter. She looks up to her trainer, and will do anything for him, including tracking down some Zero Number named Ren! When word gets out that Ren escaped from Xaki when he tried to bring her back to the community, Nia sets out to avenge the dishonor done to her trainer. Meanwhile, Ren is getting more attention from class playboy Hiro.

When Takeya rescues Ren from DearS dominatrix Barker Rubi, the trauma has caused her to lose her Japanese language skills. The cure? A little R&R, of course! They take a class trip to the resort town of Bousou, where the beach bum DearS Ayu tries to help Ren recover with a game of high-flying beach volleyball.

The new school term has started for our heroes and between needing to help Ren get changed into her uniform and Hiro-kun still making all the moves on the oblivious alien, Takeya's plate of stress and trouble is nicely topped with a surprise visit from Miu who is desperate to return his sharp-pen to him.

Hiro never seems to be able to escape his feelings for Ren. Day in and day out, he is haunted by the endless possibilities of being with her. Meanwhile, Takeya's father has other uses for Ren. Is she the key to spare all mankind and save the DearS in the process?