Sainan High

Sainan High is the school where all of the main characters (except for Mikan) study. As the series progressed, more and more of Rito and Lala's friends enroll in the school, usually girls. A running gag in the series is that the female characters in the series do not have difficulties in enrolling. This is because Sainan High's perverted principal accepts any cute girl that enrolls there. Sometimes, the principal would even invite other cute girls to go to his school (i.e. Riko). However, there were times where a male character was able to enroll easily in the school as well, like Ren who enrolled in the middle of the year. A reason for this could be that the principal's pervertedness does not pick any gender (like in one case where the principal chased Run, so she transformed into Ren, in hope that the principal would stop. However, the principal said he was okay with that too).

Students
The first ones to be introduced as students of Sainan High were Rito Yuuki, Kenichi Saruyama and Haruna Sairenji. In the second chapter, Haruna's female friends, Risa Momioka and Mio Sawada, were also introduced briefly. Then, by the fourth chapter, Lala also enrolls in Sainan High to become closer to Rito. When Haruna toured Lala around the school, another recurring character was introduced, Taizou Motemitsu, the pitcher of the baseball team who's notorious for hitting on girls then suddenly rejected and exclaimed by his posse. By the twentieth chapter, one of Lala's childhood friends, Ren Elsie Jewelria, also enrolls in Sainan High to become closer to Lala. A few chapters later, three more girls were introduced, Saki Tenjouin, Rin Kujou and Aya Fujisak, all three being one year level higher than Rito and his friends. Later, Ren's counterpart, Run, also enrolls in the school despite Ren's being enrolled there already.

On Rito and Lala's second year, another female character was introduced, Yui Kotegawa. Then, the ghost, Shizu Murasame, also enrolls in the middle of the year after Dr. Mikado gives Shizu an artificial body.

In To LOVE-Ru Darkness, a few more students join Sainan High. Two of them are Lala's twin sisters, Momo and Nana. Momo and Nana enrolled in Sainan High because Momo would like to keep an eye on Rito and his girls, so that her Harem Plan may succeed (she just convinced Nana to join her in enrolling). Another one is Mea Kurosaki, who joined Sainan High under the orders of Nemesis, so that they can blend with the Earthlings, at the same time keeping an eye on Golden Darkness. The last of the ones who have enrolled in Sainan High so far, is Yami, who joined because Mikan convinced her, and pretended that she did it because it would make Rito's killing easier.

Staff
The most prominent staff in the series is probably Ryoukou Mikado. She is the school doctor, who also happens to be an alien. She is also a close friend of Rito and Lala since it is she that they consult whenever they have alien problems. The second most prominent staff is the unnamed principal of the school. The principal would usually only appear to chase girls or to accept the cute girls into his school. So far, there is only one known event where the principal actually acts like a principal during Chapter 26 of To LOVE-Ru Darkness where he suspected Haruna of being drunk, to which he gave a stern look to. The third most prominent staff is Rito and Lala's homeroom teacher, Honekawa. He is the only seen teacher who actually discusses something in the classroom. In To LOVE-Ru Darkness, Dr. Tearju Lunatique replaces Honekawa as Rito and Lala's homeroom teacher. The least prominent staffs are Sasuga, the tennis club's advisor, and Naruiwa, a teacher in the disciplinary team.