Kagami Junichirou is known as a Genius Physicist. He wrote a thesis at a young age of 17 and it was even published by "Nature" a prominent science magazine. After college he devoted himself to being an Otaku and a NEET. Updating his Anime Blog, aiming for #1 ranking. He claims to have a disease that makes him do ONLY what he wants to do. Desperate to get him to do something with his life, his little sister manages to get him a job as a teacher at his Alma Mater.

Yotsuba Mitsuru, the day before his 17th birthday, is dumped for the 30th time. Remembering a promise with his best friend, who shared his birthdate, made 10 years before, he goes to the park to meet him, when a flash of light knocks him out just as he thinks he sees his friend. He awakens in the hospital and discovers he's been given a second chance at life… with a few strings attached.

With his phrase "don't you dare make girls cry," Makoto Tobita has failed his 30th confession, but that won't stop him. Promising to do anything for the girl who smiles at him, no matter what it is, what will happen now when the alien fighting - giant girl, Mana Eimiya, is in love with him?