Kasumi is the addedPhantom Thief to the royal addition. While she doesn’t join your party until very late inPersona 5 Royal, your interactions with her start much sooner. Kasumi is an honors student at Shujin and is a gymnast. Kasumi is very shy and is always training for her next competition, as her status at the school rides on it.
Related:Persona 5: Royal: Hardest Bosses, Ranked
**This post contains SPOILERS for Persona 5 Royal.**Kasumi is also a unique confidant, as you are only given five ranks to progress through in the early parts of the game. She had a twin sister, Sumire, who passed away after competing with her. Kasumi’s confidant line is mostly centered around her trying to get her confidence back, as she hasn’t been doing well in recent competitions since her sister’s death. After completing her confidant, the rest of her character progression is saved for the bonus third semester.
After finding out that Kasumi was a patient of Dr. Maruki before the events of the game, it would make sense she would be greatly influenced by his new reality. As you progress through the early sections of the palace, it is revealed that Kasumi has been influenced by Maruki long before the events of the game, and she isn’t even Kasumi.
Kasumi is Actually Sumire
The big reveal is that it was actually Kasumi who died in the car accident. Kasumi was the more successful one of the two, and Sumire blamed herself for her sister’s death. After her sister’s passing, Sumire began to see Dr. Maruki, who was able to use only a little of his personas' power unknowingly at the time. Through his persona, Maruki changed Sumire’s heart, making her believe she was Kasumi.
Sumire believed the world would have been better if her sister was still alive, and she wanted to take her place to make her parents proud and carry on Kasumi’s legacy. This change explains the sudden change in “Kasumi’s” competition scores and confidence. Sumire was now pushing herself to reach the same level as her sister, but this only led to more internal conflict. When Sumire first remembers that she is Kasumi, she even goes as far as to fight the Phantom Thieves to continue in her fake reality as Kasumi.
Sumire had been living the life of Kasumi since before the start of the game, and after learning the truth, she gets stuck between the two personalities and starts to lose herself. As Joker progresses through the third semester, Sumire can finally come to terms with her sister’s death and accept who she is.
After the reveal, you unlock the lastfive ranks of Sumire’s confidant line. In these ranks, she is open about why she wanted to be Kasumi and how she wants to now live her life to the fullest as Sumire, as that is what Kasumi would have wanted.
