Iroha Nijiue's design was heavily inspired by Kise Yayoi from the anime series "Smile PreCure!", as LINUJ had been inspired to create original characters similar to his favorite characters in other media. When the game first began, LINUJ thought this was easy to notice due to lack of development. Iroha's crybaby personality was one of the aforementioned similarities to Kise. Her first design was directly based on Kise, but with certain changes to make her design her own. LINUJ later redesigned Iroha when coming up with ideas for the story, before Void was officially created. At the time, Iroha wore a pair of boots instead of shoes, and her skirt had a different pattern that was removed later on. When more of the story was created, LINUJ began to start the process of redesigning Iroha, as well as many other characters, coming up with a design that was closer to what her finalized design was: the only difference before she received her final design was the pattern on her socks.

LINUJ has stated that Iroha is his favorite character from the series, but had attempted to be as unbiased as possible with her involvement and fate. During Chapters 3 and 4 specifically, LINUJ began to have more fun when writing the dialogue for her during the later part of the series and eventually reached a point where he didn't think much about what she was saying, as Iroha "doesn't think about what she's saying" from his perspective. He also worried that many people wouldn't like her, but was surprised when she later began to gain popularity in the Korean and Western fandoms.