hoshi nanami
Nanami is the undergraduate research assistant with whom Kitajima has been partnered for five years. They first met while Kitajima was on a date with Yonamine, during which Nanami introduced herself and won the doctor's approval by suggesting a perfume to her. As she is vibrant and adept at translating scientific data into relatable terms, Nanami compensates for Kitajima's own inadequacies. It becomes obvious as the series progresses that the chirpy little assistant is one of the few people Kitajima could be considered close to. Similarly, Nanami has a great deal of respect for the woman she refers to as sempai (or m'am / doc in the English dub).
This happy little partnership comes to an abrupt halt when Nanami is revealed to be a Gillard Army spy sent to infiltrate the ISDA. She proceeds to exploit her understanding of Kitajima in order to secure Toa for her own purposes. Nanami however, finds it difficult to brush aside the time she has spent with Kitajima — a woman she truly cares for and respects.
At first this affection simply manifests itself as an inability to kill Kitajima when spiriting Toa away (which Garnet is particularly unimpressed with). Later on, the true nature of Nanami's concern for Kitajima becomes apparent when she decides to assist Toa in order to avert the destruction of Earth (which she inadvertently triggered by taking Toa to Mars).
Toa: Mother has abandoned the earthborn dragons, along with mankind. But there's still time if I act now! If my voice reaches Mother--
Nanami: I don't care what your mission is. I just want to know if you're able to save Earth.
Toa: I don't know. But... I want to protect the one I love. That's all.
Nanami: The one you love... Sempai... Save Dr. Kitajima!
It is then that Nanami makes a critical choice. She decides to double-cross Gillard and remove the CSS shield on Toa in order to help Earth. Or more specifically, her beloved. This decision does not come without sacrifice — Garnet appears and shoots Nanami dead seconds after she releases the CSS shield. Her final word as she dies is "Sempai" ("Doctor" in the English dub). Horrified by what she has witnessed, Toa screams just as the CSS is reinstated. This scream is all it takes to alert Jin to where she is being held and Nanami's violent death is not in vain. Earth averts disaster and Kitajima finds herself safely under the protection of Nozaki.
Despite betraying Kitajima, Nanami redeems herself in death by saving the woman (and planet) she cares about. Sadly, Kitajima is never fully aware of how much her assistant cares for her, nor does she ever learn of Nanami's ultimate fate.