Miu Shiun'in

Mia Shiun'in (紫雲院美宇 Shiun'in Miu) is a character in Yu-Gi-Oh! ARC-V manga series. She is the deceased younger sister of Sora Shiun'in.

Past
Not much of her past has been revealed, but according to Sora, Miu had a weak sickly body and was hospitalised as the result. At one point before the story, her sickness took the toll on her and she eventually passed away.

Yūya & Yūri vs. Sora
During Sora's Duel against Yūya, Sora purposely threw his photo with Miu for Yūya to see and made up a sob story that Reiji has taken her as a hostage and the president threatened to kill her if he doesn't capture Yūya, so the Phantom will sympathized and allow Sora to win. This plan unfortunately was foiled by Yūri who was easily able to see through his lie and then ripped the photo once Sora admitted this. The photo itself turned out to be a switch for a trap that will work once the photo was destroyed as a countermeasure in case his lie was exposed.

Dream
After Sora was defeated by Yūya, losing his consciousness in the process, he was saved by Ren. While he was unconscious, Miu appeared in his dream, telling Sora to wake up and asking if Sora has forgotten about her, which Sora answered that he hasn't and he will never forget about her.