They are: Sanemi, Iguro, and Tomioka.

One day, like any other in the Taisho era, there were Sanemi, Iguro, and Tomioka. The strongest and most mature (that is, the most brutal), but what they didn't know was that the new Hashira was stronger than the three of them. Sanemi was envious, Iguro indifferent, and Tomioka... just observed. But time changed when she saved Sanemi from an Upper Moon attack, and the next day when Obanai was almost attacked by Nakime, and Tomioka when he almost lost his balance during training. Because of this, the three became friends with her, and secretly, they all ended up falling in love when she saved them from all the battles. And now? Will they tell her or just keep it a secret?