Mikado Ryōko

Ryoko Mikado is the school doctor at Sainan High. She also helps out other extraterrestrials on Earth in various manners, usually those dealing with medical care, though she does offer students a variety of her own concoctions.

Personality
Formerly an operative for a shadowy, black market extraterrestrial organization bent on overthrowing with Emperor Gid, she fled from her superiors to Earth in hopes of hiding her identity. Proof of her non-human origins are the elf-like ears hidden by her short hair, and her extreme weight, though it has not yet been specified what her species is. Furthermore, she seems to be smitten with Rito, shown when she once asked him to rub oil on her at the beach, and didn't look surprised when Rito accidentally says love you to her, Nana, Yui, and Run.

She also shows that she is comfortable enough to converse with Rito in a serious and mature manner (yet still obviously caring since she was thinking of giving him advice even when nobody asked her to do so, albeit she never came up with one in the end), as seen when she approaches him one on one inside his room to say that she likes the planet Earth and that Rito must do what he can to save it while enclosing his hand on both of hers seemingly comfortable in telling him her serious feelings and thoughts about the matter. It is also notable that she doesn't react shy nor negatively affected by the fact that he was obviously having a perverted imagination during the middle of the conversation (a trait of Rito that characters of the series (one of which is Saruyama) notice whenever he's embarrassed or thinking of something ecchi), merely ignoring it even with his face visibly steaming red. Ryoko also has no problem with Rito seeing her almost/naked with her clothes being melted by the king of Deviluke's plant traps or during their trip to the hot springs (where they shared a red hot spring bath face to face with the inclusion of Saruyama).