Haruna has shown to have a great fear of the supernatural, especially of ghosts. However, when the local ghost, Oshizu Murasame, returns to the living, via an artificially-built body from Dr. Mikado, Haruna and Oshizu quickly became good friends with each other. Oshizu learns of Haruna's feelings for Rito, and became very supportive, though not entirely helpful, for Haruna's success.
When Rito told Lala about his feelings towards her and Haruna, Lala tries to bring them together, because if Rito marries Lala, he will become the next king of Deviluke and Earth laws will not apply to him, making polygamy legal for him, so the three of them can be together.
In To Love-Ru Darkness, Lala continues to push Haruna and Rito together, although Haruna is confused for her reason in doing so. Soon, Momo told her about polygamy being a common thing in space, and the possibility that Lala and Haruna can both marry Rito together. Haruna currently doesn't know what to do with this newfound possibility.