IF, along with Compa is one of Neptune's first friends. They first met her when she fell from the Neptral tower. Since then, the three of them have been a solid trio, though nowadays, they do have to their separate ways due to their occupation. Neptune can easily rely on IF when she needs. IF believes Neptune to be lazy and selfish akin to a spoiled child, but she does trusts Neptune to get the job done when it counts. Since Gamindustri is usually peaceful, IF is sometimes tasked to get Neptune to work in the first place.
IF is one of Nepgear's closest maker friends. She was able to kick start Nepgear's transformation into her HDD in HDNmk2. IF cares for Nepgear, shown in the anime by preventing her from recklessly charging into Arfoire's trap.
Compa is IF's childhood friend. They are best friends with very different personality and are the first two to meet Neptune. IF plays the role of a protector to Compa. She is comically obsessed Compa with different incarnations of IF having pictures of her sleeping, refusing to share Compa with the other makers or wanting her to be an idol to take down Neptune.
Histoire and IF have a good relationship. IF works for the guild so she is entrusted with many tasks for Planeptune.
IF was Rei's officer, in charge of seeing Rei serve out her sentence of helping to rebuild Planeptune. IF was strict to Rei, even though Rei was completely unaware of her actions, but she does let Rei take breaks.