Soapies

Soapies is a femslash ship between Mahiru Koizumi and Hiyoko Saionji in the Danganronpa series.

Canon
Even though Mahiru is the same age as Hiyoko, she treats her as a younger sister, such as helping her with her clothing and taking baths with her. She was the only one that Hiyoko referred with respect. Mahiru can sometimes be annoyed with Hiyoko as she is being constantly dragged around by her, but is very patient with her.

Later, it's revealed that Hiyoko was one of Mahiru's best friends during her time at Hope's Peak Academy as well, Mahiru stating she loved her as well and accepting Hiyoko calling her "Big Sis". Despite their friendship, Mahiru was involved in Hiyoko's mischievous plot which included aphrodisiacs. Hiyoko later comforted Mahiru after Sato's death.

After the events of the Tragedy and Killing School Life had ended, and Mahiru and Hiyoko awakened from their comatose state, they are seen happily chatting together, and later celebrate on the ship together with Mikan and Ibuki.

In Danganronpa 3 relationship chart, Hiyoko tells Mahiru that she loves her, and Mahiru replies that she loves Hiyoko too.

According to Kazutaka Kodaka, Hiyoko's school memories with Mahiru are very precious to her, explaining why she became close with Mahiru even after losing her memories in the Neo World Program.